There are seven
bows including the rearmost. Counting the holes probably won't help you too much as the front two are different than the center four (which four are adjacent to the roof supports); and the rearmost has a different style hole than the front two.
This is the rearmost - it just goes into the round hole (which unlike the front two, the rearmost one has no "lock" to keep the bow from moving).
Trying to post a photo for you but the "attachment manager" isn't appearing - I'll try posting from the "imgur":
Hopefully it's clear from there, that the ends of the bow simply sit in there and there was no other retention for the bow. I imagine this way you could pull the headliner rearward (as the front bows cannot rotate towards the rear) and then the screw in trim would hold the thing in place from there.