No Self assessment gives you % of correct, but on real MCAT, you just get a scaled score. Something like:
Physical science: 15, 99.9+ percentile
Verbal Reasoning: 6, 20-30 percentile
Biological Science: 15 99.9+ percentile
Combined: 36, 97+percentile
Percentile means how much percentage of MCAT takers scores lower than your score, not % of correct answers.