Saw X Trap

I saw the eyeball vacuum trap in saw x and it took me sooo long to figure out why the guy was screaming.

[for context the guy in the chair has to turn a dial all five times before the vacuum sucks his eyes out, but when he turns the dial one of his fingers gets pulled up to a 90 degree angle or whatever]

anyways I couldn't figure out why he was in pain because that's how my fingers move- but I'm hypermobile and that's not how non-hypermobile people's fingers are supposed to move <( _ _ )>