I've written to Uber support for clarification a few days ago and got a reply affirming the referral promo ($20 subsidized for 1st ride) is still on going. They sent me a link : http://www.driveuber.sg/referrals/ rider referralI think the promo for $20 already ended so riders will get $10 and you will get $5. Sorry my bad.
However if they have keyed in any other promo code prior to their ride it may depend on when they keyed in their promo code it could be $10 or $20. This happens when you tell them to key in your promo code it will say "promo key already applied".
I have never used my DRIVER promo code. I will use my rider promo code as I do take UBER rides when I send my car for servicing or to the airport and I get a $10 or $20 credit when I recommend to my pax.
Anyway I just tell them to key in a promo code and they will get SOME credits. Usually they will tell me how much they get
I have trouble keeping up with the promos too.
Did you read their latest newsletter on the guaranteed rates. There are some changes to how the calculate the acceptance rates.