7x the bet
I think it's 9x.
No, it's 9x win or lose.
As Stunna said:
So if you bet 1 BTC at 2x, hit the jackpot, and win, you get 2 BTC back from winning and 9 BTC back from the jackpot for a total of 11 BTC back, or a 10 BTC (10x) profit.
If you bet 1 BTC at 2x, hit the jackpot, and lose, you just get 9 BTC back from the jackpot which is a profit of 8 BTC (8x).
In both cases you're getting 9x from the jackpot.