There are promotions and credits, depending on when you signed up what the offer was, if you did $20+kaleb a while ago you would have seen $20 credit plus $20 promotion, separate offers, but now when you sign up/refer it's a $30 promotion (they seem to have gotten rid of credit offers,for good reason, but I'm hoping for a return)
ETA: you would be best off logging in on regular uber.com to see what you have under payments, all should be there