Do they not teach math in your country. If you use 1% of bankroll as max bet you get an exponential decay in bankroll that never reaches 0.
To teach you this its easier in a chart form. The bankroll is on the Y-axis and the winning bets in a row is on the X-axis. You can see that it never reaches 0, although it does reach close enough to 0 at some point.
This means you can always payout the full winnings of the user regardless how lucky they are, the worst case scenario is that the user cashes out the entire bankroll and you have nothing left. You will always be able to pay what is owed if you use this method.
The reason is "commercial" not "technical". We have started with 20 BTC max. payout for a "reason", and commercially we are doing good. This issue has been discussed before:
https://bitcointalk.org/index.php?topic=973765.msg11441671#msg11441671 so there is no need for us to answer it again and repeat same things over and over again.
as admitted, the manual was taken from dean's site but links were later link was removed from our interface.