Just got back from my third attempt 550.
Not sure what happens with me at the real exam. Took last two gmat prep scored 660 (Q47 V35) and 680 (Q45 V 37) few days ago. Used OG book, did every problem, went over mistakes. My first Gmat score was 490 in Feb, studied hard, took kaplan score, scored 450... and now 550
Used
MGMAT book for SC. Took the kaplan course (useless in my opinion, save 1500 for a vacation after your gmat is better)
Here are the list of scores I got in practice
590 Power Prep 1
620
MGMAT
600 Kaplan 3
600 Kaplan 4
580 Kaplan 5
570 Kaplan 1
620
MGMAT 2
Kaplan 7 630
Power prep 1 660
Kaplan 5 (known as ultimate) 620
Power Prep 2 680
I honestly thought I will score for certain in the 600s, if not hit 680-700. I was a bit anxious in the begining, but later I was fine. Finished both sections in time.
Any thoughts??