I don't actually have a question nor useful to say about this.

I don't understand it, but I'll figure it out, and it's the only thing I don't understand rn, like that I know of, so I'm just going to post it and see what comes out of it, because it's not pol stuff and I prefer real math.

Feel free to talk about M generally and X(M) independently.

That's actually what I was looking for but I can't find a pdf that looks nice.