Originally Posted by Iride01

BR-R317's? Probably written on the backside of the brake body.

https://si.shimano.com/api/publish/s...009-02-ENG.pdf

https://si.shimano.com/api/publish/s...001-26-ENG.pdf

https://si.shimano.com/#/en/search/Keyword?name=br-r317

If you can't get it adjusted, then either you are just missing something or the rotor is too worn or the wrong one. But I have a hard time imagining one too worn or too thin so probably that's unlikely.