Can you explain the "Advanced-->Conditions-->Filter" and Summary Chart in Segments?

I have two images attached, and the only difference is that the "Filter" is "sessions" in one and "users" in another. Can someone explain how this affects the Summary graph on the right side? The sessions on the summary chart are much higher (25,826) when using "users" as the filter than "sessions" (12,096). Thanks for any help!

This is due to the hierarchy of the Google Analytics data model. When you are filtering for users, the right panel includes all users who have had at least one session according to your condition. The higher session figure you see are the total amount of sessions of these users for given your time period. Not all of these sessions will comply with your condition because you have filtered at the user level.

Here is a link to Justin Cutroni's post (a Google Analytics evangelist) that explains this hierarchy well: http://cutroni.com/blog/2014/02/05/understanding-digital-analytics-data/