@runiggyrun prettymuch covered it. When they say "challenges the accuracy of the evidence" it often looks like the author is attacking the premise. In the example above, Mary attacks John's statistics (i.e. 90% is NOT accurate).
Internships are prettymuch irrelevant. LSAT & GPA combined weight ~90% in terms of your admissions chances outside of Y/S & assuming you're not a URM. The only softs that significantly help are Rhodes, Olympian, etc.