.

The Q and V scores are determined first, then your score out of 800 is determined based on the Q and V scores. The Quant score isn't determined based on your 760 overall score. So it would make more sense to ask "how did I get a 760 with a Q49/V42?"

The Quant and Verbal scores you get are rounded off to an integer. But your total score out of 800 is determined based on the Q and V scores before they are rounded off. A Q49/V42 normally produces a 750 score, but in your case, you might have had scores something like 49.4 and 42.3. Because you were slightly over 49 and 42, your total score can be ten points higher than other test takers with the same Q/V split after rounding.

A 760 is a fantastic overall score (congratulations!), and a Q49 will be more than good enough for any program you apply to. The Quant percentiles are skewed these days for reasons you can read about elsewhere, and you shouldn't be concerned about them.