You can set the day of the week your pay period starts. You can also set the cycle to weekly, bi-weekly, monthly, or 1st to 15th and 16th to end of the month. To do this, go to the Settings page in Business Setup and scroll down to the Staff section. These settings will be used as your pay period for the Compensation Report.
You can also decide if commissions should be based on the post-discount or pre-discount values. Read more here.