In the past, when recruiting regularly, hs and transfer prospects all have numbers listed. After signing with you, if you currently have a player on your roster with their number, they'll be assigned/made to pick a new number.
With the transfer portal feature however, I had two players who transferred in with the same number as players currently on my roster, and they were not given a new number meaning I had duplicates. Noticed after thinking my point guard was all over the floor making plays everywhere haha. Changed it in commissioner mode but wanted to point it out!