SAP CATS - how to assign a personnel number to each employee

All,

Clients wants to capture Subcontractors Timebooking in CATS . To be precise I am unable to understand the following given by SAP help.

http://help.sap.com/saphelp_erp60_sp/helpdata/en/6 4/40048a470211d189720000e8322d00/content.htm

1. You do not need to assign a personnel number to each employee

One activity is often performed by several different persons at different times. Creating a separate HR mini-master record for each of a vendor’s employees would therefore generate a vast amount of work.

Instead, you can assign several employees, or several groups of employees, the same personnel number.

Please let me know ,how to use this concept in SAP .

Thanks ,

Irene