Do you have many files/folders on your desktop?
Strange, don't know where the extra 29+ Gb are coming from then. From what I believe, Apple Music doesn't count towards your iCloud storage costs.
I had the same problem a few weeks ago.
Several gigs of memory has been falsely reserved.
I called support and it seemed to me that this problem is not uncommon.
They asked me to go through the usual iCloud-problem-solving procedure (sign-out - sign-in).
This didn't help, so I called again, got transferred to a higher-level service employee who just deleted the reservation.
This fixed my problem.
Apple Support had to do it.Is that something they have to do? Or it can be done manually from the computer.