You will see the following fields after generating usage for Digital Sanborn Maps:

Unique Visitors
Number of visitors from a specific IP address. This means if 10 people visit from one IP address inside a library, this only counts as 1 Unique Visitor.

Visitors
The number of times a page is visited regardless of IP address. This would correlate to the total number of sessions.

Pages
Number of times a page is visited.  This does not include hits to images or components used by these pages (ie. scripts, stylesheets, etc).

Hits - Counts any hits toward a page used by the website (including images, stylesheets, scripts, etc).