I don't know about Kaplan
but PR's tests are adaptive like the real thing. Your score will depend on two key things, as far as right/wrong answers go: how early in the test your wrong answers are, and how hard those questions were. The GMAT is weighted toward the beginning of the test, so the first 12-15 questions or so are the most important. If you get them right, you get harder questions. If you get them wrong, you get easier questions and your score goes down.
So look at where your wrong questions were to figure out why there was a score discrepancy.