Create operand values for operand &1

What causes this issue?

By specifying a <DS:DE.ERSATZWERT>replacement value</> for operand &v1&
in the rate category for the installation, you cause this operand to be
proposed for maintenance in the installation facts. The proposal is
valid for the interval &v3& -- &v4&.
You have not defined operand values for the operands for the entire
period.

System Response

How to fix this error?

If the operand is a <DS:DE.INDIMUSS>required operand</>, you must
specify an operand value.
If the operand is an <DS:DE.INDIKANN>optional operand</>, it is
optional to specify an operand value.

Error message extract from SAP system. Copyright SAP SE.