Beltpacs can’t share the same beltpac number on a base and you can’t over write the beltpac number on the base with another beltpac.
Let say you have two bases. Base A and base B. Your beltpac is registered to base A which designates it as beltpac 3.The designate 3 remains exclusive to that particular beltpac indefinitely. However if you registered that same beltpac to base B the base will assign the beltpac the next available number in its registry giving it a new beltpac number. So then later you decided to use the beltpac on base A again it will need to be re-registered to base A. Base A would assign the beltpac the next available sequential beltpac number in its registry. So then there would be two beltpac assignments for that one beltpac on base A.   Side note: If you clear base A’s registry the beltpac will not connect to the base however designate 3 remains in the beltpac until its registered to a base.