Possible causes are:
Overtime calculation is set
Setting "Employee"＞ Employee type setting > [Edit] of target category> Calculate day's overtime work " Overtime start time "」
Working hours that meet the conditions are treated as overtime.
Overtime working hours are fixed
Setting "Employee"＞ Employee type setting > [Edit] of target category> Calculate day's overtime work [Detail] button＞「Overtime start time」
However, if you are registered for a time longer than the scheduled time , the overtime will be counted only after the registered time is exceeded.
*This item counts working hours that exceed the registered hours as overtime hours.
The handling of overtime hours is set
Setting "Employee"＞ Employee type setting > [Edit] of target category> Calculate day's overtime work [Detail] button＞「Extra Hours Work allocation type」
If "Fixed" or "Overtime" is selected, it will be treated as fixed or overtime.
*This item is for setting which aggregate value should be used when overtime work hours (work hours outside the schedule) occur .