You're correct. I was just trying to reframe the question as posed by OP.

I stated in other comments that I'm pretty sure Advantage Pay has to cover the entire purchase.

I've seen 25c discounts for advantage pay. I suspect they are using that as a type of loss leader to get people to sign up. Because ~15 cents would probably be the break even.

When I initially signed up they did give an additional 30c off per gallon for, I think it was a month.