Never heard that Stake is offering deposit bonus since they came in this gambling industry. You can always ask their live support to make sure about the information your read anywhere outside their own website/forum. Even if it is real, it is just a common bonus and you will have to wager 40x before you are able to withdraw. However I think it is not official from stake, or I guess it is something like a special bonus for those who register with a referral link.