The requests your analytics never saw
A script reports the visits it was allowed to report. Nemel sits at the edge, where every request is visible, and ties each one to the event in your analytics with a single thread.
Two numbers come out of that position and out of no other: how much of your traffic never reached the script at all, and how much of it no person sent. Your analytics keeps doing what it does; Nemel tells you what its numbers are a share of.