The joke is that Graham's number is so incomprehensibly, mind-bendingly MASSIVE that the tier list for ranking its digits is completely empty! It's like trying to count the number of times your professor says "um" during a lecture—except Graham's number has more digits than there are particles in the observable universe. SQUARED. THEN RAISED TO THAT POWER AGAIN. Even if you spent your entire life writing down just ONE digit per second, you wouldn't even make a microscopic dent in it. The universe would experience heat death, be reborn, and die again approximately 10^100 times before you finished. The tier list is empty because ranking every digit would be like trying to name every grain of sand on every beach... on every planet... in every galaxy... in every universe in the multiverse!