@Tom-and-Amy0 When a current or past guest is granted a refund, the amount is deducted from your next upcoming payouts, rather than debited directly from your payment method. In this case, the booking is in the future, and therefore you haven't been paid for it yet. If you agree to it, what should happen is that you simply don't receive any of the payout that the long-term cancellation policy entitles you to. (BTW, I strongly recommend paying attention to the details of this policy if you're going to continue to take bookings of one month or longer - a "Superhost" is naturally expected to be up to date on essential facts of the platform that have been in place for several years).
The booking is cancelled anyway, so you are by all means free to decline the guest's refund request. If you'd like to make a counter-offer, you may use the Resolutions tool at airbnb.com/resolutions , at your own leisure. But there's no reason for you to feel backed into a corner by someone who is already in breach of contract.