Please explain the numerical rating system. Thank you.
It is a rating system that uses numbers to represent relative likelihood of victory.
It’s roughly the glicko-2 (as opposed to glicko-1) rating system as outlined by a pdf on this page: http://www.glicko.net/glicko.html
It’s essentially a modified ELO system with a few bits and bobs to make it more accurate (the most important being the existence of a Ratings Deviation variable).
In go, rank numbers are estimates for finding a proper handicap for an even game. So if two players have ranks that are 5 numbers apart from each others, they should have pretty much the equal chances on winning when weaker player gets 5 handicap stones.
The actual ranks start from 30 kyu to 1 kyu, after which comes 1 dan to 9 dan.
You can think that 30kyu “knows the rules of the game” and 1kyu being “almost a strong amateur” where dan players are “strong amateurs”.
So ranks are basically just a tool to help players find balanced games.
I should point out that this would display in a game, review, chat column etc. as 10k. That’s because “9.3k” is considered as “0.3k weaker than 9k.”