Q. What does Fiction [S] mean?

When you see the Call number / location of a book is followed by an [S] this means the work is a collection of Short Stories.  

Short Stories are usually filed under the title of the work (minus any leading articles, such as "A" "An" or "The")  unless the collection was created by a single author. 

Example:

Louisa May Alcott's Short story collection is filed under Fiction Alcott [S]

The World's Best Short Stories is filed under Fiction World's [S]

There is a large red S on the spine of books containing short stories.