Comparison: minimum number (&1) of comparative rents not met

What causes this issue?

The <DS:DE.REAJCOMPADJM>number</> of comparative rents
entered in <DS:SIMG.REFXV_TIVAJSPECCOMP>Customizing</>
for the adjustment rule was not reached.
This may be for one of the following reasons:
The comparative group of apartments does not contain sufficient
comparative apartments.
No contracts exist for own objects in the comparative group of
apartments (vacancy).

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?

Assign more comparative apartments or internally rented objects to your
comparative group of apartments.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.