Fake or not, its not really that unreal.
Not really unreal enough. It is possible as far I can tell chance is 1:10 000 - so it is not even Lotto level unreal win. But again, 18 BTC is not really close to PowerBall level of jackpot.
If the player had really won that bet, the profit of that bet should be 9989*0.002 = 19.978 btc instead of 19.98 btc. So this is clearly fake.
That is why I don't trust anyone who claims that they won amazing money anymore. Too many trolls and fakes.