Excellent question--and one that puzzles so many who prep for the GMAT.
The reason that your scores/percentiles differed (despite the number of questions answered correctly) is due to WHAT questions you answer correctly versus the number or percentage you answer correctly.
Both Kaplan's and the Test-Day GMATs are CATs--Computer Adaptive Tests--that work on this basis: the more higher-difficulty questions that you answer correctly, the closer your score and percentile resemble that level of difficulty (regardless of how many overall questions you answer correctly).
I know this may be confusing or frustrating, but the GMAT is fashioned this way to challenge critical thinking. Thus, CATs try to push us to the highest levels of our abilities. Hope this helps you!