Back up size - persistent growth

Incremental backups just means that unchanged database files are not backed up as a new copy every single time, only the changes are, and automatic Roon backups are definitely incremental in that sense.

You can restore a backup from a specific time stamp.
That doesn’t mean that it’s possible to restore only parts of it.

That said, something seems off for @John_Kustak1 and no idea what’s going on