SAP Message RU521 - Only &1 &2 for previous operation &3 from order &4 has been confirmed

Diagnosis
V1 v2 were confirmed as the yield quantity and rework quantity forthe preceding operation/sequence &V3& of the subordinate order &V4& inthe collective order.
The quantity that you currently want to confirm (=sum of yield, scrapand rework quantity) is greater than the quantity confirmed until now(&V1& &V2&). That is not permitted.

Procedure
Check the yield-, scrap- and rework quantity created.