SAP Message /ISDFPS/CL_FDPDA_SLD063 - & dependent plans exist at serial number level

Cause,,
The planned quantity at material-number level is insufficient. &V1&dependent plans already exist at serial-number level.

System Response
The system does not execute the plan, nor does it adjust it.

Procedure
You can either increase the planned quantity at material-number level orreduce the planned quantity at serial-number level.