No one can tell you, sorry. It varies so much person to person.
But..... In my mind.... If you are at the 600 range, I would recommend postponing the exam. It is very unlikely you will be able to pull a 50 increase in a two week period. I know this isn't what you want to hear.
I would say not to take the exam until you start scoring in the 670 ranges on practice exams. CONSISTENTLY. This will leave you a little breathing room if you make dumb mistakes (which everyone does).
A 50 point increase is pretty significant - its a jump of 14% in terms of pecentiles (from 600 to 650) (600 being 70%, 650 84%) - thats not an easy jump. That will take study and time.
Just to illustrate my point about how everyone is different - stolen from one of my other posts:
Quote:
One friend of mine took it "for fun" and scored a 780. He just wanted to see what he would get. Wasnt even interested in grad school at that point. He didnt even know the format. Another friend of mine studied on the train during his trip to the exam, for about a half hour, scored a 720. Another friend of mine took a 9 week prep course, studied at least 30 hours a week, for all 9 weeks, and scored a 540 despite scoring 650's on practice exams. He then studied another 120 hours on top of that and pulled a 680. In the end, he put in well over 400 hours.
One girl I know studied for seven months and got a 720.
I studied for about 15 weeks, averaging 25 hours a week for 9 weeks, (225 hours), scored a 640, and then put in another 6 weeks pushing 30 hours a week, (180 hours) before I scored a 730. All told, I put in about 400-500 hours of study over a period of 15 weeks. I took somewhere in the neighboorhood of 20 full length practice exams. That's about 80 hours of exams. My story is here:
https://www.gmatclub.com/phpbb/viewtopic.php?t=30030