Percentage-off coupons apply to the original reservation accommodation fare. If the accommodation fare is changed after a guest makes a reservation for your listing, the coupon price will be applied to the original fare price of the reservation that the guest initially booked.
For example, let's say you have a 10% off coupon for a listing with a nightly accommodation fare of $100. The guest books the reservation for this accommodation at fare price. You then make a price adjustment after the reservation is booked to make the accommodation fare of your listing to be $150 per night. The 10% off coupon will apply to the original $100 accommodation fare price and not the $150 price.