GMAT PREP Help!!?

Hey guys, I've studied extensively with the Kaplan GMAT prep materials and am consistently scoring 550-580 on their practice tests. I recently found my officially GMATPrep cd from the GMAC and took both the tests, scoring a 710 and 760. I have no idea which is accurate, if either. If anyone has a clue where I stand, I'd appreciate some help. Thanks.