Hi milanfan21,
First off, a 660/Q48 is a strong score (it's right around the 80th percentile overall), so it could be enough to get you into your first-choice School. Scaled Score 'combinations' are not 'fixed', so overall scores can vary a bit (based on rounding and when the Exam was administered). GMAC has publicly stated that the Official Score that you earn on Test Day is within +/- 30 points of actual ability, so Business Schools know that a 660/Q48, 670/Q48 and 680/Q48 are essentially the same score. As an aside, you seem astounded that the Official Score doesn't match the predictions of 3rd-party GMAT companies. Have you considered the possibility that those companies don't necessarily have information that is 100% up-to-date and accurate?
GMAT assassins aren't born, they're made,
Rich