Use a number field for the entry value of &

What causes this issue?

The value you have entered in this field is not a number.

System Response

The program has terminated because no calculations
can be performed using this value.

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?

For calculations, use fields of type I, P, or F.

Error message extract from SAP system. Copyright SAP SE.