It has been discussed too many times but there is still no clear formula to calculate the bonus because Stake is not informing about it publicly. What we know is the aspects that affect our bonus such as VIP rank, wager and lose/win. The lose/win seems to be one with biggest effect for the bonus because if you lose more = bigger bonus. About your case, we do not know how much you usually get for the monthly and how much you get this month. If you can share some more information such as your VIP level, wagering statistic and overall profit statistic, maybe we can know why you get more.
Yeah we're tired of discussing this one but there's no way to get the exact formula and so far we have only guessed how much we will get in each bonus. To be honest, recently the bonus I got was less than what I expected even though my gaming activities are different every month but the bonuses are almost the same. Since the update of the base bonus amount, some of my friends have not played actively I don't know if Stake is aware of this or they don't see the change in player activity.
By the way, last Saturday I was very lucky to be one of the winners in the Giveaways on the stake forum
I get free balance even I don't watch live stream, did any of you get it too? I know to participate users must post Stake username and the right color, but this time I prove the right color does not have any impact because I just post a username and win, I don't know why they should post a username + color they even have to edit the post if they guess the wrong color lol.
. I have no idea who is the owner of this estimator but the owner should have better formula to calculate the bonus estimation. 
