Rear-Most Arm Rest Nut? '82 GTSi

Trying to remove the door panel to service these slow windows.

I've gotten everything, but the rear nut (I'm guessing it's a nut) off of the arm rest.

The first two (the one under the opener and the one in the middle) were 10mm. This one is so buried I can't tell if it's smaller, bigger, not a nut... anyone know off-hand what size it is and if it is indeed a nut?

Thanks!

 

NVM had to use some locking pliers to get it off. It's an 8mm but it was so worn it wasn't turning.