This may occur when using the decimal display (1 hour 30 minutes is displayed as 1.50).
When the decimal display is selected, the daily working hours are displayed to the second decimal place. How to handle the third decimal place,
Settings " Others」＞ Options settings ＞
Display setting "The handling of the third decimal place for 10 decimal display":
You can select from rounding down, rounding up, and rounding off.
The monthly totals are not accumulated working hours displayed on a daily basis, but the working hours in the display period are first aggregated in minutes and converted to decimal numbers for display. Therefore, an error may occur depending on the fraction processing to the third decimal place.
Example) When the third decimal place is rounded up
Working hours 7 hours 40 minutes →7.66666...→7.67
If this is for 5 days, it will not be 7.67 × 5 = 38.35, but 7 hours 40 minutes × 5 days = 38 hours 20 minutes → 38.33333... → 38.34.
From the above, it is recommended that you temporarily change the display format to sexagesimal to check the accurate aggregation by the minute.