By default, Purlem will assign a random 4-digit identifier to the end of duplicate PURLs. For example, if we had 3 contacts each with the name "Joe Smith," we would be provided the following PURLs:
domain.com/Joe.Smith domain.com/Joe.Smith5234 domain.com/Joe.Smith6903
You also have control to modify how duplicates are made unique, by using a contact field as the unique identifier. To update the value used for duplicates, go to your Dashboard and select edit next the Campaign you would like to update. Scroll down to the Duplicates section, and adjust there.