How to create the org unit for the new organization

Scenario :

I have two organizations. Supremo power and ACME contractor.

While trying to create the new organization bucket for ACME contactor, even upon choosing the organization as ACME contractor, I could able to choose only the Supremo power in the org unit / Bucket field and its created under supremo power only.

expected solution :

need to create the organization unit under the ACME contractor and should select the ACME contractor in the list.