Open Time and Attendance.
Open Punch Editing.
Select the desired employee from the drop down box at the top left of the screen.
Select the proper pay period, Current or Previous.
Select the punch in question from the available punches in the middle of the screen.
Click the Details button on the bottom of the screen. It is the third button from the left.
In the Punch Details Window it will show you what rules are affecting your employees calculations.