Give the user the following information: 

To determine a student's percentile rank, the course calculates their Elo rank and compares that rank to all other users. The number of eatrightPREP® users, the difficulty level of the questions the user has answered, the number of questions the user has answered, how other students answered the same questions, and the amount of content the user has/has not completed all factor into the percentile rank. 

For example, let's say a student completes 40 practice questions (out of the 400+ in eatrightPREP®) with a 94% average on the first day they use the course. Because they're compared to all other students, including those who have finished the course, they may not necessarily be in the 94th percentile.