Guest accepted a $50 refund from Airbnb resolution center but only received $15?!

For some reason when a guest booked for the month of February the system overcharged them one extra night. WIth fees and my cleaning fee I was confused about how much extra they were charged but essentially they paid $770 instead of $700, and I figured they got charged an extra day of about $50. There was no way to rectify it at the time that I could find, (picking less days) and because of the timing and my lack of knowledge I didn’t want to ‘send an offer’. I Just thought i’d contact ABNB and rectify it.

but then come to find out there is like no way to Contact ABNB. so following advice on the forum I went through the resolution center and send the guest $50. THey received it, but only actually got $15 from ABNB!!! so I know they don’t’ return their fees, but this was the system mistake and they were overcharged for single night they did not stay. So my only way out of it it seems is to pay the other $35 to the guest over paypal?? or what? I think that would work unless ABNB already took a full $50 form me? But I’m kind of disappointed they’d take the fee from the guest and not give me that option, as it doesn’t resolve anything!

I have no idea as this was my first guest. As it happens a guest booked the next longer month (March ) without any overcharge issue.

Please advise? Tks.