I don’t do brightshare so am not familiair with their policies, but various programs have rules where they deduct things.
Sometimes bonuses, sometimes royalties, and all kinds of other fees.
Actually I think that they all deduct one thing or another – it is just that with some you can see it and with others it is hidden in the comission calculations.
I am not a real friend of being charged for bonuses and usually avoid such programs – making an exception for some RTG casinos because they convert nicely.