You are one of those users who get the bonus so basically you can check yourself to know what kind of bonus is this then you can share it here.
Most of the time, Stake send a cash reward and you have said yourself that the bonus is $10 so basically you have claimed it, right?
If you are wondering on what event/promotion related to this bonus, usually there is information in the email you get but in other case Stake may give random bonus for those who are actively playing in specific type of gambling games.