diff --git a/lib/delayed/monitor.rb b/lib/delayed/monitor.rb
index c6080e2d..d2979693 100644
--- a/lib/delayed/monitor.rb
+++ b/lib/delayed/monitor.rb
@@ -97,7 +97,7 @@ def max_age_grouped
     def alert_age_percent_grouped
       oldest_workable_job_grouped.each_with_object({}) do |job, metrics|
         max_age = Job.db_time_now - job.run_at
-        metrics[[job.priority.to_i, job.queue]] = max_age / job.priority.alert_age * 100 if job.priority.alert_age
+        metrics[[job.priority.to_i, job.queue]] = [max_age / job.priority.alert_age * 100, 100].min if job.priority.alert_age
       end
     end
 
diff --git a/spec/delayed/monitor_spec.rb b/spec/delayed/monitor_spec.rb
index 849b801f..5ee86890 100644
--- a/spec/delayed/monitor_spec.rb
+++ b/spec/delayed/monitor_spec.rb
@@ -112,19 +112,19 @@
     let(:p10_payload) { default_payload.merge(priority: 'user_visible') }
     let(:p20_payload) { default_payload.merge(priority: 'eventual') }
     let(:p30_payload) { default_payload.merge(priority: 'reporting') }
-    let!(:p0_workable_job) { Delayed::Job.create! p0_attributes.merge(run_at: now - 1.hour) }
+    let!(:p0_workable_job) { Delayed::Job.create! p0_attributes.merge(run_at: now - 30.seconds) }
     let!(:p0_failed_job) { Delayed::Job.create! p0_attributes.merge(failed_attributes) }
     let!(:p0_future_job) { Delayed::Job.create! p0_attributes.merge(run_at: now + 1.hour) }
     let!(:p0_working_job) { Delayed::Job.create! p0_attributes.merge(locked_at: now - 3.minutes) }
-    let!(:p10_workable_job) { Delayed::Job.create! p10_attributes.merge(run_at: now - 2.hours) }
+    let!(:p10_workable_job) { Delayed::Job.create! p10_attributes.merge(run_at: now - 2.minutes) }
     let!(:p10_failed_job) { Delayed::Job.create! p10_attributes.merge(failed_attributes) }
     let!(:p10_future_job) { Delayed::Job.create! p10_attributes.merge(run_at: now + 1.hour) }
     let!(:p10_working_job) { Delayed::Job.create! p10_attributes.merge(locked_at: now - 7.minutes) }
-    let!(:p20_workable_job) { Delayed::Job.create! p20_attributes.merge(run_at: now - 3.hours) }
+    let!(:p20_workable_job) { Delayed::Job.create! p20_attributes.merge(run_at: now - 1.hour) }
     let!(:p20_failed_job) { Delayed::Job.create! p20_attributes.merge(failed_attributes) }
     let!(:p20_future_job) { Delayed::Job.create! p20_attributes.merge(run_at: now + 1.hour) }
     let!(:p20_working_job) { Delayed::Job.create! p20_attributes.merge(locked_at: now - 9.minutes) }
-    let!(:p30_workable_job) { Delayed::Job.create! p30_attributes.merge(run_at: now - 4.hours) }
+    let!(:p30_workable_job) { Delayed::Job.create! p30_attributes.merge(run_at: now - 6.hours) }
     let!(:p30_failed_job) { Delayed::Job.create! p30_attributes.merge(failed_attributes) }
     let!(:p30_future_job) { Delayed::Job.create! p30_attributes.merge(run_at: now + 1.hour) }
     let!(:p30_working_job) { Delayed::Job.create! p30_attributes.merge(locked_at: now - 11.minutes) }
@@ -144,9 +144,9 @@
         .and emit_notification("delayed.job.failed_count").with_payload(p0_payload).with_value(1)
         .and emit_notification("delayed.job.working_count").with_payload(p0_payload).with_value(1)
         .and emit_notification("delayed.job.workable_count").with_payload(p0_payload).with_value(1)
-        .and emit_notification("delayed.job.max_age").with_payload(p0_payload).with_value(1.hour)
+        .and emit_notification("delayed.job.max_age").with_payload(p0_payload).with_value(30.seconds)
         .and emit_notification("delayed.job.max_lock_age").with_payload(p0_payload).with_value(3.minutes)
-        .and emit_notification("delayed.job.alert_age_percent").with_payload(p0_payload).with_value(1.0.hour / 1.minute * 100)
+        .and emit_notification("delayed.job.alert_age_percent").with_payload(p0_payload).with_value(30.0.seconds / 1.minute * 100)
         .and emit_notification("delayed.job.count").with_payload(p10_payload).with_value(4)
         .and emit_notification("delayed.job.future_count").with_payload(p10_payload).with_value(1)
         .and emit_notification("delayed.job.locked_count").with_payload(p10_payload).with_value(2)
@@ -154,9 +154,9 @@
         .and emit_notification("delayed.job.failed_count").with_payload(p10_payload).with_value(1)
         .and emit_notification("delayed.job.working_count").with_payload(p10_payload).with_value(1)
         .and emit_notification("delayed.job.workable_count").with_payload(p10_payload).with_value(1)
-        .and emit_notification("delayed.job.max_age").with_payload(p10_payload).with_value(2.hours)
+        .and emit_notification("delayed.job.max_age").with_payload(p10_payload).with_value(2.minutes)
         .and emit_notification("delayed.job.max_lock_age").with_payload(p10_payload).with_value(7.minutes)
-        .and emit_notification("delayed.job.alert_age_percent").with_payload(p10_payload).with_value(2.0.hours / 3.minutes * 100)
+        .and emit_notification("delayed.job.alert_age_percent").with_payload(p10_payload).with_value(2.0.minutes / 3.minutes * 100)
         .and emit_notification("delayed.job.count").with_payload(p20_payload).with_value(4)
         .and emit_notification("delayed.job.future_count").with_payload(p20_payload).with_value(1)
         .and emit_notification("delayed.job.locked_count").with_payload(p20_payload).with_value(2)
@@ -164,9 +164,9 @@
         .and emit_notification("delayed.job.failed_count").with_payload(p20_payload).with_value(1)
         .and emit_notification("delayed.job.working_count").with_payload(p20_payload).with_value(1)
         .and emit_notification("delayed.job.workable_count").with_payload(p20_payload).with_value(1)
-        .and emit_notification("delayed.job.max_age").with_payload(p20_payload).with_value(3.hours)
+        .and emit_notification("delayed.job.max_age").with_payload(p20_payload).with_value(1.hour)
         .and emit_notification("delayed.job.max_lock_age").with_payload(p20_payload).with_value(9.minutes)
-        .and emit_notification("delayed.job.alert_age_percent").with_payload(p20_payload).with_value(3.hours / 1.5.hours * 100)
+        .and emit_notification("delayed.job.alert_age_percent").with_payload(p20_payload).with_value(1.hour / 1.5.hours * 100)
         .and emit_notification("delayed.job.count").with_payload(p30_payload).with_value(4)
         .and emit_notification("delayed.job.future_count").with_payload(p30_payload).with_value(1)
         .and emit_notification("delayed.job.locked_count").with_payload(p30_payload).with_value(2)
@@ -174,9 +174,9 @@
         .and emit_notification("delayed.job.failed_count").with_payload(p30_payload).with_value(1)
         .and emit_notification("delayed.job.working_count").with_payload(p30_payload).with_value(1)
         .and emit_notification("delayed.job.workable_count").with_payload(p30_payload).with_value(1)
-        .and emit_notification("delayed.job.max_age").with_payload(p30_payload).with_value(4.hours)
+        .and emit_notification("delayed.job.max_age").with_payload(p30_payload).with_value(6.hours)
         .and emit_notification("delayed.job.max_lock_age").with_payload(p30_payload).with_value(11.minutes)
-        .and emit_notification("delayed.job.alert_age_percent").with_payload(p30_payload).with_value(100) # 4 hours / 4 hours
+        .and emit_notification("delayed.job.alert_age_percent").with_payload(p30_payload).with_value(100) # 6 hours / 4 hours (overflow)
         .and emit_notification("delayed.job.workable_count").with_payload(p30_payload.merge(queue: 'banana')).with_value(1)
         .and emit_notification("delayed.job.max_age").with_payload(p30_payload.merge(queue: 'banana')).with_value(4.hours)
     end
@@ -201,7 +201,7 @@
           .and emit_notification("delayed.job.failed_count").with_payload(p0_payload).with_value(2)
           .and emit_notification("delayed.job.working_count").with_payload(p0_payload).with_value(2)
           .and emit_notification("delayed.job.workable_count").with_payload(p0_payload).with_value(2)
-          .and emit_notification("delayed.job.max_age").with_payload(p0_payload).with_value(2.hours)
+          .and emit_notification("delayed.job.max_age").with_payload(p0_payload).with_value(2.minutes)
           .and emit_notification("delayed.job.max_lock_age").with_payload(p0_payload).with_value(7.minutes)
           .and emit_notification("delayed.job.alert_age_percent").with_payload(p0_payload).with_value(0)
           .and emit_notification("delayed.job.count").with_payload(p20_payload).with_value(8)
@@ -211,7 +211,7 @@
           .and emit_notification("delayed.job.failed_count").with_payload(p20_payload).with_value(2)
           .and emit_notification("delayed.job.working_count").with_payload(p20_payload).with_value(2)
           .and emit_notification("delayed.job.workable_count").with_payload(p20_payload).with_value(2)
-          .and emit_notification("delayed.job.max_age").with_payload(p20_payload).with_value(4.hours)
+          .and emit_notification("delayed.job.max_age").with_payload(p20_payload).with_value(6.hours)
           .and emit_notification("delayed.job.max_lock_age").with_payload(p20_payload).with_value(11.minutes)
           .and emit_notification("delayed.job.alert_age_percent").with_payload(p20_payload).with_value(0)
           .and emit_notification("delayed.job.workable_count").with_payload(p20_payload.merge(queue: 'banana')).with_value(1)
@@ -228,8 +228,8 @@
 
         it 'emits the expected alert_age_percent results' do
           expect { subject.run! }
-            .to emit_notification("delayed.job.alert_age_percent").with_payload(p0_payload).with_value(2.0.hours / 3.hours * 100)
-            .and emit_notification("delayed.job.alert_age_percent").with_payload(p20_payload).with_value(4.0.hours / 1.year * 100)
+            .to emit_notification("delayed.job.alert_age_percent").with_payload(p0_payload).with_value(2.0.minutes / 3.hours * 100)
+            .and emit_notification("delayed.job.alert_age_percent").with_payload(p20_payload).with_value(6.0.hours / 1.year * 100)
         end
       end
     end