sites like rollbit,stake etc will never tell you the exact calculation they use to calculate bonuses ;; so that they can reduce these whenever they feel like it.
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I don't think that's the reason, so they can reduce it at will. It's more [like the representative explained] it is determined by the system and was calculated by many different factor that they can't specify it down. For example, for user A, the bonus is calculated from 10% of his loss because he's currently losing <10,000 USD, 3% of his wager because he wagered 250,000 USD, and x% of the house edge and other factors. As you can see, his number will constantly change depending on these three factors only, it'll change with the game he played, with the outcome of his bet, and the amount he placed. Can someone really zeroing on the exact formula to calculate a bonus if it kept changing?
These sites highly advertise themselves as being provably fair and have detailed algorithms/calculations as to how their games are fair