Helo fellas

I'm a little confused coming from Fanuc's PMC over to Mitsubishi's

My first hurdle is understanding how Parameters get their PMC adress. For example when looking at currently used parameters, RB87.0 I can see is adressed as M9590 But RB111.0 can be found as M19690. In-between this enourmous leap there are a ton of objects that are not RB parameters. what gives? How do i find out which M adress to use to "check" RB100.0 if it's not at this day present in the ladder?

Tia