Refunding a guest who cancelled, how do I know the correct amount?

[Elias11]

I just joined, and before I really got to grips with anything, a guest had booked. It was very inconvenient, because I didn't quite understand instabooking, had not put up a 2 day minimum stay (I'm renting my room out while I'm away, and I have a friend coming over to clean/hand off keys, etc. So it is really inconvenient if he has to come there every day), and hadn't put the price where I wanted it. I am really new to this, btw, I have never even booked a room before. 

I messaged the guest and explained my situation and he understood, and was kind enough to agree to cancel. He asked if I would pay his service fee and I thought that was fair, he then told me the amount, which he claims is 20% of the total amount I was going to get (including VAT and charge). Can that be right? And since it is impossible to attach anything through the message, how can I be sure that is the correct amount?

Regards,

[Sandra126]

Personally, I would honour the booking and move on, implementing the rules you want for future bookings. You can see what the service fee is yourself simply by looking at your own place but without actually booking it, Airbnb will show the calculations.