Wait if you use a discount coupon on a discounted item and get a 100%+ discount does that mean you'll get money from it, or is it completely impossible to discount the discount?
I'm pretty sure you can't use coupons on sale items
But if you could, the discounts multiply, not add.
So for example, if you had two 50% off, that would be 75% off (.5 * .5 = .25)