Employee Timesheet; calculating +/- hours worked

Hi!

I'm trying to setup a basic Employee Timesheet on excel and I'm have an issue - I'm also not very proficient with excel. I'll attach my working Excel sheet to make thing clearer.

What I want to do is to automatically calculate the +/- hours worked by an employee; Column G
A full day would be 8.5 hours. So, if someone works 10.5 hours, then they have + 2 hours (2 hours overtime). Conversely, if someone only works 6.5 hours, then they have - 2 hours (2 hours minus/under-time).

Each +/- would be calculated for the respective day.

If there are any questions, then please let me know.

Also if there is a better way to enter in work times, then I'd appreciate all inputs. Inputs in regards to other issues are also very welcome.

Attached is my excel sheet.

Best,