Empty Mailing List when Created with Target Group

[PPPP]

I'm using 6.0.1. I created a Target Group that matches on 2 custom fields. When I use the same criteria to make sure I have inputted correctly in under Recipients->Overview, I got a number of records. However, when I go to Target Groups -> Overview -> "My_Target_group" -> create mailinglist from this target to create the mailing list, the list is empty. Does anyone know why?

Edit: One more question. Where do I specify what Mailing List the Target Group filters on?

[PPPP]

To add more info, I noticed if I go to Recipients -> Overview, in the "Target group" drop down menu, if I select the target group I just added and click OK, it would get 22 items. However, if I look at the Mailing List created from the Target Group, there is no item.

Any idea?