It is an on-chain game and 0.0002 BTC is used in mining fee.
No, it's a "transaction processing fee". Look at Bet #530 or any other bet that lost.
The bet amount is 0.0006BTC, and the transaction that was given is 981f3689d2ef7e8f477948ea17287eb90472ab189d3c803cb05478b076a3bb64
There are 2 outputs - one of 0.0008BTC, and one of 0.008BTC. It would seem logical to assume that the 0.0008BTC was the bet, right? Why would they need to pay the miners fee if the bet lost? Actual 12x payout for this example btw, not the 16x they advertise.