The Primary Order determines the order in which you want the inactive clients sorted on first.

Client ID Select Client ID if you want the clients on the report to be sorted by the Client ID.
Client Name Search Select Client Name Search if you want the clients on the report to be printed alphabetically based on the Client Name Search field in the client records.
Primary Timekeeper Select Primary Timekeeper if you want the clients on the report to be sorted by the Primary Timekeeper of the client.
Secondary Timekeeper Select Secondary Timekeeper if you want the clients on the report to be sorted by the Secondary Timekeeper of the client.
Originating Timekeeper Select Originating Timekeeper if you want the clients on the report to be sorted by the Originating Timekeeper of the client.
Category Select Category if you want the clients on the report to be sorted by the Billing Category assigned in the Client File.
Last Activity Date Select Last Activity Date if you want the clients on the report to be listed based on the last date where information was entered for the client. The clients with the oldest activity will be listed first (i.e., descending date order).