Future note to self after two hours of cleaning up old, no longer needed files on the Synology: The reason Time Machi...

Future note to self after two hours of cleaning up old, no longer needed files on the Synology: The reason Time Machine reports that it doesn’t have enough room to perform a backup, even though 1+ TB suggest that it clearly does, is because the Time Machine user account has hit its quota, but TM doesn’t know about the user quota so won’t delete old backups to make room.