There could be two explanations:
- Your holdings may not be current for that particular item. We encourage you to make sure holdings information is current in WorldCat to ensure correct exposure through WorldCat.org
- The item might share the same title but may exist in a different format or edition, and thus be catalogued as a separate item (e.g., a large-print or audio version of a book).
OCLC addresses the issue of duplicate records for the same title whenever it is identified, so that users are able to recognize and choose from among multiple-item records.