The link: https://apidocs.symantec.com/home/SAEP states that parameter "pageSize" is the number of results to include on each page. By default the API call will return 25 clients per page. The customer is looking for a way for all the clients to be returned in a single list.
Server 2012 Sepm 14.2
Adding the pageSize parameter to the API call can achieve the desired results.