explain bar graph

docs/user-guide/continuous-aggregation/usecase-example.md

@@ -81,7 +81,7 @@ GROUP BY
     bucket;
 ```
 
-The above query put the data from the `ngx_access_log` table into the `ngx_distribution` table. It calculates the total number of logs for each status code and packet size bucket for each time window. The `date_bin` function is used to group the data into one-minute intervals. The `ngx_distribution` table will be continuously updated with the aggregated data, providing real-time insights into the distribution of packet sizes for each status code.
+The above query puts the data from the `ngx_access_log` table into the `ngx_distribution` table. It calculates the total number of logs for each status code and packet size bucket (in this case, since `trunc`'s second argument is -1, meaning a bucket size of 10) for each time window. The `date_bin` function is used to group the data into one-minute intervals. The `ngx_distribution` table will be continuously updated with the aggregated data, providing real-time insights into the distribution of packet sizes for each status code.
 
 # Conclusion