Scenario:
When the Productivity Detail report is run, it does not show the correct Billable hours for the date range selected.

Cause:
Web TimeSheet can track the productivity hours on a monthly, quarterly and yearly basis only. Hence, when the Productivity Detail report is run with a certain date range, which is less than a month, it will always show the billable hours for the whole month, considering the date range is less than a month.
If the date range covers around 45 days or less, the report will show data for the two months within which the selected date range is covered in the report.

Resolution:
This is the normal behavior of the application, and is working as designed.