I'm sorry to hear about your experience, but the good news is that you do appear to have a higher score in you! Keep working hard and a 700+ could be very very close. Unfortunately there is little to no chance that there was an issue with your particular test that brought your score down
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If the answer to any of these questions is "No" then this might be the problem:
Did you take your practice under timed conditions? (Taking practice tests without a timer can greatly inflate your score. Not only are you getting questions right that you may have missed on a real test, but you a training yourself to answer questions too slowly)
Did you only take the GMAT prep practice tests once? (seeing only a few repeat questions can greatly inflate your score)
Did you take the AWA with the practice tests? (Taking practice tests without the AWA cuts out a whole hour of test taking. On test day, your stamina could be depleted after the AWA, whereas when you studied you would be going into Quant fresh b/c you didn't take the AWA)
Did you use all 75 minutes in both sections? (They give you 75 minutes for a reason. If you ran out of time, or had too much time left on the clock, you missed out on getting questions right that you missed)
Did you leave any answers unmarked? (Leaving answers unmarked when the time runs out leads to a HUGE penalty. Its better to guess if you have to)
Did you take 10-15 seconds to double check questions to make sure you got them right? (If a question seemed too easy, it probably was. Double check, make sure you take every word into consideration. Double check your work, and make that 10 seconds count. Work these double checks into your studying, and factor them into your 2 minute per question calculation)
Did you read my post here to help you with the intangibles?: https://gmatclub.com/forum/10-tips-to-improve-your-score-app-with-no-extra-studying-124393-20.html
Don't let one bad test destroy your motivation. Just as you are writing about your disappointment today, you could be writing about your excitement a month from now. Visualize yourself writing that debrief with the test score your looking for, and keep your nose in the books. Good luck!
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