The name & has already been used

What causes this issue?

The name &V1& is already being used for the standard hierarchy in
controlling area &V2&.
The name must be unique in order to avoid errors when you process the
standard hierarchy later.

System Response

The system did not accept your entry.

How to fix this error?

Choose a name for the standard hierarchy which you are not using for
another controlling area.

Error message extract from SAP system. Copyright SAP SE.