Rule "average" chosen for non-numerical attribute

What causes this issue?

The selection rule 'Average' has been determined for the attribute &V1&
. But the system cannot calculate an average because the format of the
attribute is not numeric.

System Response

The derivation is assigned the status 'Carried out with error'.
If the derivation is static, the system saves it, but does not make
changes to the master data or the classifying attributes of the
receiving batch.

How to fix this error?

Correct the receiving condition record.
If the derivation is static, repeat the derivation or correct the
derived values manually in the receiving batch.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.