No, base reward mean only the reward you roll, not including the bonus when you got 100% by play multi or 1000% exchange from RPs.
Your thought is right. Whenever your ref win 200$ by roll the number 10000, you will receive 100$.
I hadn't thought of that way when they changed the wording, I took base reward just to mean the lowest payout. If you're right then my refs have been very unlucky lately, none rolling 9986 or over for a long time.