Right now we are allowed a max payout of 1.5% (per Moneypot's investment bankroll) per single bet. So that would mean you can win 219411048.21 (satoshis)BTC or to simplify: 2.19 BTC per bet. So to answer your question, it is based on max payout not max bet.
Just to avoid confusion, the restrictions are based on
max profit. For a dice-style bet, the investors will only allow you to attempt to take the same percent of the bankroll as the house edge.
The limit per app is based on RHavar's discretion for us he agreed to 1.5% but this is something that could go up or down as our site matures.
I'm not quite sure where this came from. MoneyPot has a function that applies the generalized kelly criterion to all bets coming in, which answers a simple question: "Is it economically rational to accept this bet?", if the answer is yes, it'll accept it. If the answer is no, it'll reject it.