Understanding Top Session Finder with Inactive sessions. (4261974)

When using the Top Session Finder, often when using the Overall stored profile, sessions that are in the database in an inactive state are showing up as the top sessions.  How can an inactive session rise to the top and be highlighted as top sessions when there might be 50 or so currently active session running at the time?

Also, usually one might use the tool to find out what sessions are bogging down the database. Why sometimes killing those inactive sessions acts like a flush and the database often times will appear to run much better  (referring to sessions that have been in an inactive state for a long time).  In the morning, sessions show up as top sessions but also have been inactive for hours.  Could it be that resources are still being held by those sessions?