You can refine your catalogue search in a number of ways to narrow your results (using the left-hand pane of the search screen).
Your results list when searching the library catalogue can include one book, that has multiple versions. In this case it is multiple editions of the book:
In this case, there are different locations for the same book. Note 'and other locations'
There can also be different formats of the same book, either on the shelf (available) showing the 'call number' or available online as an eBook (Check for online availability).
Books, journals, kits and DVDs in the USC Library are shelved by subject. Call numbers on books and journals appear most often on the spine or on the front cover if the spine is too narrow.
Here's a sample call number, with explanation of how this affects the way the item is shelved:
LB - describes general subject area; shelved alphabetically
2395 - narrows subject area; numerical order (whole number)
M44 - subject area OR author (alphabetical then decimal order)
2012 - year of publication, numerical order