RBAC question

hi every one i tried rbac and i made
1- role called GizaRoot
2- group called gizagroup
3- added privlage autherization called "m.k"
/usr/sbin/useradd:dflt:(m.k,*):0/0//:dflt:dflt:dflt:

i assigned the role to group and add user to that group then su to user and tried to use the command
privrun useradd maxim it worked and every thing ok but i don't under stand why it uses the euid=0 and ruid=0 and i assigned only to group not user i tried to make the line like this /usr/sbin/useradd:dflt:(m.k,*)://107/0:dflt:dflt:dflt:
but it didn't work so i want one to explain to understand and thanks