Found this commented out in the start screen html. The values are hard-coded, and there's no code to retrieve live values, but it shows what Uber are possibly thinking of: I wonder if those stats are an actual snapshot of some point in time?
Well this looks quite cool But it is definitely no snapshot..I don't think there were ever 54321 players online at the same time yet (that's probably more like the total playerbase right now). Also, the number looks quite like something someone thought of for fun. 5 4 3 2 1