Procurement BU on Internal supplier registration on Redwood UI from RSSP

Summary:
Hi Experts,

I see there are list of Procurement BU's which appear on on Internal supplier registration form on Redwood UI from RSSP, Can someone please help me with the setup from where list of values default?

On supplier master work area registration page, I could see that the Procurement BU list appears on the basis procurement agent access to user, but not sure on Internal supplier registration on Redwood UI from RSSP as am unable to restrict the Proc BU.

I have tried creating a requester user with only one BU access to test the scenario, But still could see multiple Procurement BU on registration form redwood UI from RSSP window.