You have a lot of strong attributes to your candidacy and the lower than expected quant score is not your application in totality. If you have time, I would try to re-take the exam as it is below the levels that admissions generally looks for. However, you do have enough "quant" in your background that admissions will not be concerned that you will not be able to handle this aspect of the program. In your application, this has to be addressed and you have to make sure that you point out how this score is not indicative of your abilities or potential.
Regardless, I still think you (with a strong application -- essays, recommendation, resume, interview, etc.) would still be a strong candidate at Johnson and Stern. HBS is going to be a long shot, as you know.
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