Merge of Assets - entering details of Parent and child Asset

HI

While Performing Merge of Assets I had enter details of Category, Location and Exp Code for only Parent asset and checked the Sum Units Check Box, but system does throws below error

so do i need to enter the details of Category, Location and Exp Code for child asset as well?

what is the process of merging so that all details of Parent asset should default to child asset including thee Units of both ( child and Parent)

Rgds

Raju