Interpreting session activity
It means there are 100 unique visting during which the request.session got modified. The unique visiting is based on per-user-browser: a user who uses Firefox and then Chrome to access your site AND having request.session modified during the process will be identified as two or more visting. Normally, there is no modification upon request.session thus no session entry will be generated. The default login page sets test flag in request.session, thus session entry will be generated for visitor, no matter whether he can log in successfully . Also, if a visitor denies cookie, his every access to the login page would generate a session entry.
I am looking at my table for django_session and would like to know what this essentially means. 
If I have 100 session entries in the past hour, does that mean 100 people have logged in in the past hour? Or does it mean something else?