&1 cannot be interpreted as a number

What causes this issue?

You have entered &V1& as a number. The Formula Builder cannot interpret
&V1& as a number.

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 a number in a number format.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.