Message SAP WTADDI653 - Additional & is invalid

Diagnosis
You want to generate data for additional &V1& only.
V1 is not recognized as an additional. it is either invalid as amaterial or is not classified as being an additional.
Note: A material can be used as an additional if it is assignedto a material type with the material type ID "Additional".

System Response
Generated data is not used for this combination.

Procedure
Check your entries.