How do I use Manage Project Properties?

I have a question about "Manage Project Properties" under RQM.

I have a user who has created a type called "Installed Software" in "Lab Resource and Channel Properties" and underneath that are items such as Application, Browser, Database etc.

When the user enters "Test Plan Environment Types" and selects the drop down on "Installed Software" in the Types column the "Set Type" option is greyed out.  If he selects "Installed Software" a new column appears listing Application, Browser, Database etc.  If he selects the drop down on Broswers then the "Set Type" option is available.  If he selects Browsers, and then tries the drop down for Netscape in the new column then the "Set Type" option is again greyed out.  What is it that causes this option to be available?

I have tried to follow the documentation here ...

http://www-01.ibm.com/support/knowledgecenter/SSYMRC_4.0.3/com.ibm.rational.test.qm.doc/topics/t_cust_tp_env_types2.html

... but it is unclear.  It talk about making something a type by adding an entry against "Machine".  There are entries such as ...

Operating System    Multiple Values Type    Operating System

... but if I try to create an entry for Netscape and select "Multiple Values Type" then I'm presented with a multiple choice list which doesn't contain Netscape so I can't create the entry.

Advice would be appreciated.