I want to clarify that what the stats are tracking are visitors and views, rather than visitors and viewers. In other words, visitors counts the number of people who visit your blog, and views counts the number of times various posts/pages are viewed by those visitors.
The stats graph at the top of the page will show how many visitors and views your blog received. The stats you see underneath show more information about the views themselves. In other words, you're seeing information about the posts and pages your visitors viewed.
I hope that makes sense! Please let me know if you have any questions about it. :)