& is not an area unit (Please correct)

What causes this issue?

The quantity unit &V1& is not a surface unit of measure

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?

Enter the correct unit of measure
or
choose a surface unit of measure using the F4 function.

Error message extract from SAP system. Copyright SAP SE.