Does the percentage given remove the same from the affiliate?

The title doesn’t really explain what I mean. If, for example, an affiliate can earn 25% from an affiliate sale and they set a coupon for 10%, will the affiliate then receive 15% of the sale, or will they receive 255 still?

I like the idea of the former, as this then means the affiliate can work out a strategy to get more sales, but with the latter it means the store has a little trouble as we lose out more.