Group help

I use GroupManager and I want to make someone admin in only one world. So i type /manuadd lonzo708 admin Metropolis and it says watch your argument count. Then it says /mangadd <user> <group> : optional [world] and I've tried about every combination of that i can think of, but i either says added you to the group admin in all_unnamed_worlds or it says watch your argument count. I use multiverse Core to make worlds if that helps at all.