The official paper tests give scoring guidelines at the end. For those that have taken these things in the past (SAT, LSAT, etc.) then the scoring formula is pretty typical. You take the number you got correct, then deduct 1/4 point for each missed question (essentially you miss 1 1/4 total for each wrong answer) which will leave you with a raw score. Then there is a chart that translates raw scores to overall scores, based on the scaled difficulty of the exam.
I agree that the exams are not perfect prep tools because they are not adaptive, but I found them superior to all sources other than the OG & GMATprep. They are official questions from real exams and provide a much better foundation for understanding what real questions call for. I also found the tests to be pretty accurate in predicting my score, far better than the Kaplan
so called CAT. I took 5 paper tests and scored between 750-780. I scored between 750-790 on GMATprep and I got 730 then 780 on the real thing.
On the Kaplan
so-called CAT...I got 590. Needless to say, that result was worthless.