In the Backups of previous versions pull-down menu, select either No limit on backups or Maintain limited number of backups.
If you choose a limited number of backups, enter the amount of backups you want the SCC system to maintain in the field which appears.
Click OK.
The SCC system makes a copy of the previous file when a user checks in a file. If the SCC system is keeping a limited number of backups, it will begin deleting the oldest version of a particular file every time the user checks that file in, after the desired number of backups has been reached.