You can't think of MCAT scores as % correct, that's just not how the exam is structured. There are numerous different versions of the MCAT given out and each has its own curve. Your percentiles are based on the % of test takers you do better than.
Example: You could theoretically get 66% of the questions right on a C/P section that was tough for a lot of exam takers and end up with a 128. You could also get 80% questions right on a relatively easy C/P section and also get a 128.
You can try to look at trends from past test takers and their FL scores, but you can only speculate at best.