So no one has showed me that option before - putting in the overrides. I am not even 100% sure what that does. 

If I put all my classes and subclasses in as overrides does that mean it will all map correctly - and allow the selected class per hour override the one I had to initally select for the person? 

I just ran Payroll today - is there a way for it go back and fix past payroll runs to map.