You want to reset the round points midway through a league.
Go to Stats/Standing Grouping (Menu > Manage > Stats/Standings > Stats/Standing Grouping).
1. Go to Teams.
2. Select a league.
3. Pencil to edit.
4. Go to Advanced section.
5. Enter a start date for Round Points.
6. Enter an end date for Round Points.
7. Save.
* You can create groups for the first half and second half. You can even have a group to see the total of round points.