You cannot set that value on the Resource Breakdown Structure (RBS) outline code}The only values that you can set are: Blank ...

{You cannot set that value on the Resource Breakdown Structure (RBS) outline code}The only values that you can set are:
Blank
Your own RBS value (^1)
Children of your own RBS value
The original RBS value on this resource (^2)
Children of the original RBS value on this resource. 

Please contact your system administrator to get Manage Users and Groups permissions if you want complete freedom to edit RBS values on all resources you have Read-Write access to.  Otherwise, please get some other user to make the RBS edits for you.