SAP Message 28056 - Characteristic &1 not alphanumeric

Diagnosis
The system syntax check discovered an error which is probably due tothe fact that the characteristic entered is not alphanumeric (CHARformat), even though only alphanumeric characteristics can be enteredhere.

System Response
The cursor marks the incorrect characteristic.

Procedure
Check the expression at the cursor. Make any necessary corrections.Please see also other possible causes of error (messages).