This is really a big money to bet with 0.5 btc on per roll. Luckily you ended up making money which is a good thing else you could have lost as well as the nature of the game is to make the site profitable then the gamblers or players. You really took the risk and played it and got it regarded as well. Well done and play safe in future as well.
Yeah, that 0.5 roll was a bit risky one, with high odds as well, dude managed to get 8 bitcoin versus 6.5 lost but that is just one picture, we do not know what happened before or after that. I am afraid its quite risky to win like that, it would have to be pretty lucky to end up in a good margin of profit, usually you end up losing a ton before you recover in those bets, like for example losing 10 times in a row but then winning like 3-4 times in 7 tries and suddenly you are closer to break even.
I have been around crypto gambling for about 7 years now so I have done all the things you could think of as strategy and I can tell you that this one is a pretty brave one, I wouldn't dare to do it. Not that it has any less chance to win or lose, they are all destined to house edge, but this one can end up losing too quickly.