glad to know that there is a bounty bug, I wonder how much is the reward

Depends on the bug. I found a bug recently about an ordering in the transactions log and got nothing. Wasn't probably that critical.

These days, unless the bug is huge like some type of seed leak or some type of major vulnerability then you will most likely not get anything.
Most sites have these bug bounties but very rarely do they pay out for typos and other minor text formating issues.
Found bugs that potentially will interfere with the safety of a gambling site and especially those that can be financially disadvantageous, will surely get a decent prize. Such bounty is exist on most gambling sites, as I know.