Enter a land parcel or a group

What causes this issue?

In real estate planning for land parcels, you can either enter one
land parcel or a group of land parcels 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 land parcel or the group, or
Enter a value in one of the two fields.

Error message extract from SAP system. Copyright SAP SE.