It seemed obvious to me from the start the whole clip goes under the stud. But then I don't know how many times it ended up with only one side under while I was trying to install it. So I knew that was too loose to work.
I thought that odd shape on the clip it might be used for clipping it in (start one side, push it over, start the other side) but no. I think it's a part of getting the danged thing back off after it's installed though.