diff --git a/src/adonisjs/public/editor/annotate/js/annotator.js b/src/adonisjs/public/editor/annotate/js/annotator.js
index 9c121757..bd084f2e 100644
--- a/src/adonisjs/public/editor/annotate/js/annotator.js
+++ b/src/adonisjs/public/editor/annotate/js/annotator.js
@@ -211,7 +211,11 @@ class Annotator {
       for (const r of a.fragments)
         ranges.push({fragment: r, annot: [a]})
     }
-    ranges.sort((a, b) => a.fragment.start - b.fragment.start)
+    ranges.sort((a, b) =>
+      (a.fragment.start == b.fragment.start)
+        ? b.fragment.size - a.fragment.size  // bigger first
+        : a.fragment.start - b.fragment.start
+      )
     for (let r = 0; r < ranges.length - 1; r++) {
       if ((ranges[r].fragment.start == ranges[r + 1].fragment.start) &&
           (ranges[r].fragment.size == ranges[r + 1].fragment.size)) {
@@ -540,7 +544,8 @@ class Annotator {
     }
     const ctcategories = Object.keys(catIndex).length
 
-    const clustering = Math.round(AnnotationMetrics.i._clusteringFreeRecall(catOrder)*100) / 100
+    const cfr = AnnotationMetrics.i._clusteringFreeRecall(catOrder)
+    const clustering = (isNaN) ? cfr : Math.round(cfr * 100) / 100
 
     if (isAnnotations) {
       document.querySelector('#memory-scores').innerHTML =
diff --git a/src/adonisjs/public/editor/annotate/js/metrics.js b/src/adonisjs/public/editor/annotate/js/metrics.js
index a8b430bd..6dc412f0 100644
--- a/src/adonisjs/public/editor/annotate/js/metrics.js
+++ b/src/adonisjs/public/editor/annotate/js/metrics.js
@@ -87,7 +87,9 @@ class AnnotationMetrics {
       else
         nc[cat]++
       let nextPos = i + 1
-      while (nextPos < sortedL.length && sortedL[nextPos][1] === sortedL[i][1])
+      // find next position of the same category or neighbor start
+      while (nextPos < sortedL.length &&
+             sortedL[nextPos][0] != cat && sortedL[nextPos][1] === sortedL[i][1])
         nextPos++
       if (nextPos < sortedL.length) {
         let sp = nextPos
@@ -115,7 +117,24 @@ class AnnotationMetrics {
 
     const ds = r - er  // deviation score
 
-    const arc = (r - er) / (max - er)  // adjusted ratio of clustering
+    const arc = 
+      (max - er == 0) ? '0/0' : (r - er) / (max - er)  // adjusted ratio of clustering
+
+    console.log('\n\n=== Clustering Free Recall ===')
+    console.log(JSON.stringify(categoriesOrder))
+    console.log('--- n = ' + n)
+    console.log('--- sorted by position')
+    console.log(JSON.stringify(sortedL))
+    console.log('--- c = ' + c)
+    console.log('--- ni')
+    console.log(JSON.stringify(nc))
+    console.log('--- r = ' + r)
+    console.log('--- max = ' + max)
+    console.log('--- E(r) = ' + Math.round(er * 100) / 100)
+    console.log('--- RR = ' + Math.round(rr * 100) / 100)
+    console.log('--- MRR = ' + Math.round(mrr * 100) / 100)
+    console.log('--- DS = ' + Math.round(ds * 100) / 100)
+    console.log('--- ARC = ' + ((isNaN(arc)) ? arc : Math.round(arc * 100) / 100))
 
     if (present != null) {
       present('\n\n=== Clustering Free Recall ===')
@@ -125,14 +144,14 @@ class AnnotationMetrics {
       present(JSON.stringify(sortedL))
       present('--- c = ' + c)
       present('--- ni')
-      present(nc)
+      present(JSON.stringify(nc))
       present('--- r = ' + r)
       present('--- max = ' + max)
       present('--- E(r) = ' + Math.round(er * 100) / 100)
       present('--- RR = ' + Math.round(rr * 100) / 100)
       present('--- MRR = ' + Math.round(mrr * 100) / 100)
       present('--- DS = ' + Math.round(ds * 100) / 100)
-      present('--- ARC = ' + Math.round(arc * 100) / 100)
+      present('--- ARC = ' + ((isNaN(arc)) ? arc : Math.round(arc * 100) / 100))
     }
 
     return arc
diff --git a/src/adonisjs/public/editor/annotate/metrics/test-metrics.js b/src/adonisjs/public/editor/annotate/metrics/test-metrics.js
index 4d745ff4..b198ff3b 100644
--- a/src/adonisjs/public/editor/annotate/metrics/test-metrics.js
+++ b/src/adonisjs/public/editor/annotate/metrics/test-metrics.js
@@ -31,4 +31,19 @@ present(AnnotationMetrics.i._clusteringFreeRecall(
 present(AnnotationMetrics.i._clusteringFreeRecall(
   [[2, 71], [2, 96], [3, 98], [2, 98], [5, 98], [5, 130], [5, 135], [3, 140], [5, 180]], present))
 present(AnnotationMetrics.i._clusteringFreeRecall(
-  [[2, 71], [2, 96], [3, 98], [2, 98], [5, 98], [7,98], [5, 130], [5, 135], [3, 140], [5, 180]], present))
\ No newline at end of file
+  [[2, 71], [2, 96], [3, 98], [2, 98], [5, 98], [7,98], [5, 130], [5, 135], [3, 140], [5, 180]], present))
+present(AnnotationMetrics.i._clusteringFreeRecall(
+    [[2, 1], [5, 2], [2, 3], [3, 4], [1, 5], [5, 6]], present
+))
+present(AnnotationMetrics.i._clusteringFreeRecall(
+  [[1, 1], [1, 2], [1, 3], [2, 4]], present
+))
+present(AnnotationMetrics.i._clusteringFreeRecall(
+  [[7,1],[3,2],[7,3],[3,4],[2,5],[2,6]], present
+))
+present(AnnotationMetrics.i._clusteringFreeRecall(
+  [[1,1],[1,2],[5,3],[2,4],[8,5],[1,6],[1,7]], present
+))
+present(AnnotationMetrics.i._clusteringFreeRecall(
+  [[5,1], [5,2], [5,3]], present
+))
\ No newline at end of file