SAP Message VHUMI502 - Batch split for material & batch & is not clear

Diagnosis
The material to be identified is listed more than once in the materiallist of the manufacturing order, even though a batch was not specified.The batch of the material to be identified therefore cannot be assignedto a material.

System Response
The batch split cannot be carried out.

Procedure
Assign one or more batches to an item of the material in the materiallist of the process order.