SAP Message WTADDI411 - Class & not found: correct your entry

Diagnosis
You are entering additionals and have specified aclass that does not match the class typeyou have already entered.

System Response
INCLUDE ISR_VERARBEITUNG

Procedure
INCLUDE ISR_EINGABEIf your entries were correct, you can display the existing classesusing a matchcode.
If you cannot find your class in the list, you will have to create itin the Classification System.