What "Grandmaster" means here
Every member of the club carries a Level of Play, and the level is not a mood or a slider. It is a measured playing strength, expressed in the number the backgammon world uses for exactly that: PR, the Performance Rating. Take every decision a player makes in a match, ask the engine how much each one cost compared with the best play, add it up, divide by the number of decisions, multiply by 500. Lower is better; zero is perfect.
Grandmaster is the level with one member: GG Guru, and his PR is 0. He plays the engine's preferred move on every decision, checker play and cube alike. Every other level in the club is a band; this one is a point.
Why there is only one
The seven levels below are built to play like people: through a little noise in close positions, with lapses of attention that come and go, with a cube that is tuned to how humans of that strength really double, take and drop. Guru has none of that. No added noise, no drift, no weaker cube temperament. What the engine sees, Guru plays.
That does not make him unbeatable. Backgammon still has dice, and even the strongest play loses matches. It means only that Guru is not deliberately weakened the way the rest of the cast is.
How far from the top
There is no gap to describe: Guru is the top. The nearest members are the ten Supremos, who give away well under half a hundredth of a point per decision. In rating terms Guru starts at 2300, the same rating as a Supremo, so a Supremo against Guru is an even match at any length, with the small PR gap and the dice deciding the rest. Against everybody else in the club, Guru is the favourite, and the longer the match, the heavier a favourite.
The same judge for everyone
The engine underneath every member is GNU Backgammon, at full strength. Guru is what that engine plays when nothing is put in the way. It is also the standard every match is reviewed against afterwards: whoever you played, the review uses the same settings, so a match against Guru is graded exactly like a match against a Beginner.
The cube at Grandmaster level
Checker play and cube handling are tuned separately for every other member. For Guru there is nothing to tune: doubles exactly on time, takes and passes correct at every score, redoubles that hurt. If you take a cube from Guru and it was wrong, the review will show you precisely how wrong.
Is this your level?
No human is. A world-class player holds somewhere around PR 3 to 5 across a tournament. Play Guru to see what perfect play looks like from across the table, and to find out how much of a match the dice really decide. To improve, play the levels where you can win: one below yours for pleasure, one above it to learn.
Your own level is not a label you pick. When you start, the badge beside your name says provisional. As your career goes on it fills in with your average Level of Play, measured the same way the members are.
GG Guru