Originally Posted by WesternSkies

You are thinking of it from the wrong angle.
You don't get 4:1 on top of pay, you get a garuntee of a minimum of 4:1. At the end of the trip if you look back at your pay, if you didn't fly enough to have pay-to-duty ratio to exceed 4:1, company will add money to your paycheck to bring you up to a minimum ratio of 4:1.
If your trip met or exceeded that 4:1 criteria on its own then it doesn't apply to you.