Observe the input format: &

What causes this issue?

The input format was not followed for a number input.

System Response

The input could not be processed.

How to fix this error?

Repeat the input. Follow the input template
&VAR1&.
Digits are represented by underscores ("_") in the template. The
thousands separators can be omitted.

Error message extract from SAP system. Copyright SAP SE.