No I did not make a mistake.
Check in mist :
enter 5e18 in bet
you get 26000000
And it's not a rate.
It's the value of diffculty in the equation.
bigNumber * difficultyMultipler % difficulty_ == 0
So the hash number * 1000 (diff multipler) has to be a multiple of 260000000 for you to win.
1 chance over 260 000.
I know solidity. I did not make a mistake.
This game is a scam.
"a multiple of 260000000" / 1 000 000 - this step is missing in your calculation
But contact the developer - he told me this.