Enter a building or a group

What causes this issue?

In real estate planning for buildings, you can enter either one
building or a group of buildings on the planning initial screen.
You cannot, however, enter both.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Either delete the building or the group, or
Enter a value in one of the two fields.

Error message extract from SAP system. Copyright SAP SE.