Nathan - I'd put a lot more stock in your GMATPrep scores than in any other scores, and if you truly need another estimate of your level, you'll get the best information from the additional GMATPrep tests you can buy from mba.com. Some of my students report similar scores between company and official tests, while others report huge discrepancies. GMATPrep is consistently the most reliable indicator.
And I don't like to disagree with Brandon, but I think this needs clarification:
VeritasPrepBrandon
That being said, Veritas tests are the next best thing. The tests utilize the same algorithm as that utilized by the gmat exam itself
Your company's webpage is careful not to say that - it says "Veritas Prep’s practice tests are built on a platform that employs Item Response Theory (IRT), the same system underlying the real GMAT". It does not to claim to use "the same algorithm" as the GMAT, because there's a huge leap from "using IRT" to "using the GMAT algorithm". There's a lot more to the algorithm than just the IRT foundation. I'm happy to discuss in more detail, but I don't want to sidetrack this thread with stuff of no relevance to the OP. But I'd add: that a test uses IRT has little to do with its value as a predictor of GMAT scores, because IRT has little to do with test validity (as that term is used in test theory).
And I hope no one thinks I'm commenting on the quality of Veritas tests (I think I've only taken the free one, so I'm not very familiar with them). I'm not - I just wanted to clarify that no tests besides the official ones use the same algorithm as the real thing.