At the suggestion of homebizseo, I installed Display Unread Posts and New Reputation Comments.

This plugin displays the actual number of posts that are still considered unread by you (and will show up in a 'getnew' search).

There is the option to count the unread posts since your last visit, or all posts considered unread. This setting reflects the divider in the 'getnew' search display.

The default is "Use Last Visit Date", but I switched this to "Count All Posts Marked as Unread". This setting made more sense to me.