Hello, please help if you can.

I have a time sheet that is in hours across columns.

User enters start time and end time. Last column
calculates the total hours worked. No problem.

When I sum the hours I get correct total hours.
The problem is, I need to subtract 40 hours from the total
hours worked. I get a nonsense value.

For example, total hours worked is 12. Then 40 - 12 = 12

Please tell me what is wrong. Thanks in advance.