Hi Cburton815,
Since your GMAT score is only 60 or so points below your score goal, there probably is not a pressing need to cancel your score. If on your next exam you do improve and achieve your score goal of a 600 (or higher), schools will be able to see that improvement, which certainly won’t hurt.
With that said, I’d like to learn more about your GMAT experience to help determine why you came up short on test day.
1) Did you get your enhanced score report? If not, could you do so and share the score breakdown from your GMAT?
2) Can you provide the dates and score breakdowns of your official MBA.com exams? When you took the practice tests, did you take them under realistic conditions (e.g. in a quiet environment, no extended breaks)?
3) What is your study routine? For how many months did you study for your GMAT and for how many hours a day? What resources did you use for your prep?
4) For how many hours a day can you study for your retake?
5) What deadlines are you targeting?