Hi,

From the employee attendance, you can calculate the employee working hours. If there is only one check in and check out per day, you can just subtract those two values and find the working hour.

If there are multiple check-in and checkouts, you can still find the working hours of the day by subtracting the adjacent check-ins and check-outs.

For the coding on the same, please refer to this module where the calculation of the employee working hours is done weekly and monthly:  Employee Working Hours

Once you get the total hours you can find the Over Time from it. Also, there is a module in the store for the automatic calculation of the Over time, you can have a look at that too: Automatic Overtime Calculation

Thanks