I see that if I configure a option under the “Preferences” tab in Newsletter “Subscription Form” it will add a checkable box under the subscription form itself that the user can opt-in or opt-out of certain types of emails by checking it or unchecking it. And there is also a checkable box in the tab in my Newsletters composition area called “who will receive it”. But what is the function of adding a “Extra Profile Fields” option? I mean it does not allow me to distinguish who will get a newsletter or not based on any of my subscribers who have chosen certain “Extra Profile Fields” options. So what is that “Extra Profile Fields” option really for?