Collection property behaves like a List when it contains only values.
Select the Portals tab.
Select a portal from Portals.
From Select DN drop-down menu, select any DN.
Under Task, click Manage Channels and Containers.
Select a container in the tree on left frame to display Edit Properties page on the right frame.
Click the Edit Values link of a property to launch the wizard.
Make your changes.
Click Close.
The edit properties page will update number of values in the list.