Scenario:
Let us say you have Productivity target set for a user as 100 hours for the month of October
User has entered 50 Billable hours and 25 Non Billable hours for the month of October.
When you run Productivity details or Productivity Summary report with Month filter set to October, it gives below data;

Billable hours= 50
Non Billable hours= 25
Billable Target =100

The above output is accurate.

But when you use date range filter instead of Month filter just incase you want to run report for 15 days (Oct 1st to Oct 15th), it is supposed to return the billable hours and non-billable hours entered by the users as of Oct 15th instead it still returns 50, 25 and 100 as Billable, Non-Billable and Billable target.

Resolution:
Data in the productivity report is by month, quarter and year. Due to this reason we cannot get data for a specific date range. To get data for a specific date range we need to use a different report, like Project Time Analysis or Project task user detail.