I scored 840 90% this time. Up from around 60% in the Apr. test.
Basically I got almost exactly the same number of wrong answers in both tests, but this time I am able to answer faster and get more correct answers so the result improved.
Really hope that the score could help me with my real bad undergrad GPA(Although I guess it might not even help.).
Good Luck to Everyone at MathGRE, and esp. Thanks for those who have helped me here.