Starting clean with an external TimeMachine drive that's full
I have multiple TimeMachine drives and found I get informed when older backups are deleted. I like that. But today, I was told the disk is full and can not do the backup.
I did move my machine to a new MacBook, then back to my old MacBook, so it is trying to do a 312GB backup. Those are likely files it already has, but from a different machine ID.
How do I simply start over with that drive?