I dont think the max score is 300. According to the tables of NBME exams, the max score is 290. Nobody knows how the test is scored, but from my understanding even getting 100% of the questions correct on the exam does not guarantee a perfect score (290 or whatever the highest number is). The reason for this is it is a scaled score and all of the scores above the mean are tied to a score below the mean. That is my understanding anyway. I know for a fact that on the MCAT if you get 100% of the questions you probably wont get a 45 and I think USMLE is the same way (that information was from someone who talked to the MCAT director directly)