You can´t. Before the ICO when PRC and BetKing were still running
on a bankroll that everyone could invest in the current bankroll was always
visible. This isn´t the case anymore and therefore you would probably
have to ask Dean about the current size of the bankroll.

My estimation of at least 500 BTC was just based on an educated
guess based on "industry standards" and the current max win (the
max win is still displayed at the site as actmyname pointed out).