It appears that the OP is a PT loader and works in CA.
I too am in the western conference, much of my time spent as a steward.
OP appears to be a M-friend employee, therefore any Sunday work is considered a 7th punch and is at double time for both PT and FT. Sunday is always a 7th punch regardless if you work Saturday or even whether you worked your entire 5 days of your 5 day schedule for the week, provided you are a M-friend employee. If he/she is a Sun-Thurs employee Friday would be considered a 6th punch and would be at 1.5x for the entire shift.
If OP is PT then overtime would start over 5 hours on any of his/her regularly scheduled 5 working days, unless there is a break of time greater than a 1 hour lunch in between shifts (as in working doubles), in which case OT starts after 8 hours per day. If you are FT, you recieve OT after 8 hours per day, regardless of whether you are over 40 hours yet for the week.
You can do the math. I believe this covers all possible scenarios.