To calculated prorated potential hours Bob takes into account the base full-time pattern as well as the expected work hours in a week and the number of days in a cycle.
In the example below, the employee is contracted for 16 hours per week and we will be working with a 21 work day cycle.

To calculate the employee's prorated potential hours:
Bob divides the weekly hours by 5 working days (The Full-Time working pattern is from Monday to Friday).
16 ÷ 5 = 3.2 hours per day
And then multiplies that figure by the number of days included in the attendance cycle.
3.2 × 21 days = 67 hours 12 minutes
For this example the employee's logged hours are less than the prorated potential hours.
Potential hours: 67 hours 12 minutes
Logged hours: 59 hours 12 minutes

Difference: 8 hours

Because the employee logged 8 fewer hours than their prorated target, Bob displays an 8 hour attendance deficit.
The attendance balance is based on the hours expected during the cycle compared with the hours actually recorded. If the logged hours are lower than the prorated target, a warning will appear.