If i have more than one group content type?

In Commons 1.3, those view headers are set programatically via the Commons Core feature because we need to use the l() function in order to create working links. Views doesn't allow you to do this from within the UI. In previous versions of Commons, we used the PHP input format for the View header, but that is never a good practice.

You could either use a custom module to alter the view, the same way that Commons Core does, or perhaps you could add an additional block, etc.