The GMAC declares the following about missing questions:

"¢ MYTH - It is more important to respond correctly to the test questions than it is to finish the test.

o Reality - There is a severe penalty for not completing the GMAT. If you are stumped by a question, give it your best guess and move on. If you guess incorrectly, the computer will likely give you an easier question, which you are likely to answer correctly and the computer will rapidly recover. On the other hand, if you don't finish the test, your score will be reduced greatly. Failing to answer five verbal items, for example, could reduce a person's score from the 91st percentile to the 77th. Pacing is far more important.

From this we can infer that for every question you leave blank, you are effectively reducing your percentile score for that section by 3%.

Quant 36 corresponds to approx 48 percentile. If you had attempted and got those 2 questions right, perhaps you could have gone up to a score of 38 with a 54 percentile.
Your overall score could possibly have been 640.

What were your practice MOCK scores? Have you done significantly worse than your baseline?

Let us know, and good luck!

Thanks for the advice albatross86

I thought my math skills would be much higher, previously I was scoring much higher.
I had been practicing lots of 600 to 700 questions.. perhaps I should have spent more time practicing questions from the 500 level..

I did a practice test very early on and got near 450, basically I have not done any math in 10yrs.
So, I did a lot of practice and did the practice test, I downloaded on mba.com, then I got over 40.
But, on test day, I was uncomfortable with the marker... It really slowed me down

Well, the school I want to get into average is under 600.. So, I will just apply there
If I retook, I think I could get a 650, but my big problems is my undergraduate GPA..
Anyway, thanks for the advice.