Why does MSAR MCAT differ from school specific websites?

I am looking through school websites on admissions stats and I and finding that the avg MCAT they list is a few points lower than the MSAR median. For example: Dartmouth website has 512 as avg MCAT but MSAR has 516. Is that because the MSAR is going by the median vs the avg (school website)? Just curious. Thanks!
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Tags: Pre-Medical - MD Source Type: forums