What are the follow topic settings on Hubpages?

When I follow a topic on Hubpages (for example “Literature”) , I will get content about Literature in my feed. I will also get content about subcategories in my feed (For example “American Literature”). For me that means that I am following the subcategory “American Literature” also. However, when I am on the page of American Literature, I get the button “Follow” rather than “Unfollow”.

How does this work? Perhaps there are different default norification settings for sublevel topics..?