1. Create a separate time sheet batch for pay types that should not affect overtime.
2. Create a calculation including both time batches.
 
OR

1. In Configuration, Pay Types, open the Overtime Pay type.
2. Select the Restrictions Tab.
3. At the bottom, change "All" Pay types to the specific pay type the overtime should be calculating for.
4. Save and close the pay type.
5. Expire the old "Overtime" from the employee record and add the newly updated "Overtime".
6. Update the Time and Attendance Batch by adding the employee again.
7. Calculate the Time and Attendance Batch.