The accounting goes as such:
1. Guest books and pays Airbnb
2. Airbnb holds this money until the reservation
3. Airbnb pays you 24 hours after the check in date
If the guest cancels, the cancellation terms kick in.
1. Guest books and pays Airbnb
2. Guest cancels and Airbnb refunds based on cancellation policy (supposed to be no more than 50% so really unclear how your guest was getting back a quarter of the money)
3. Airbnb hangs on to the remainder of the money until the date of check in
4. Airbnb releases remaining funds owed to you 24 hours after the check in date
If you choose to refund the guest more money, it comes out of your pocket now in the form of deductions on current payouts. You will receive the remaining money, if any is owed to you, at check in date.