Hi Vijay,
If you accounted for the major 'variables' that you'll face on Test Day (the same time of day, taking the CAT away from your home, taking the FULL CAT - including the Essay and IR sections, taking the CAT on a desktop computer, same general amount of sleep the night before, etc.), then this score is reasonably accurate. Again, the more you deviate from the specifics of Test Day, the more your score can 'inflate.'
GMAC has publicly stated that a Test Taker's Official Score is typically within +-30 points of actual ability, so your prior practice CAT scores and Official GMAT score had some 'overlap' (by extension, your actual ability at THAT time was probably around a 670).
GMAT assassins aren't born, they're made,
Rich