The data on the side says,
Average Rating: 1304
Average Glicko RD: 123
White Wins: 49.4%
Black Wins: 46.9%
That compares to 343.252 players of 'standard' chess (traditional chess, SP518 RNBQKBNR). These numbers are all for 'turn-based' chess, i.e. correspondence chess.
The numbers of players for 'live' chess, i.e. crossboard chess, are
It's not surprising that the player count for chess960 is the smallest of the five playing categories. Even so, it's roughly equivalent to total USCF membership.