I am thinking that the "earn 8,000 points" figures big time into this. I have gathered that for STAYs # 2 and #3 combined, the maximum points I will earn is the 8,000. Not sure how the bonus points figure in, but I am guessing they don't. The deal caps points earned at 8,000.
So, I guess the bigger/real question is - why did my account balance only go up 1,908 points??