Unless you start before a pick starts (and can then pick your work), you'll be on the extra list. More than likely, your days off will be during the week. Time of day work depends on the particular slot but work on the list is assigned in report time order. So slot 1 would get the first open job, slot 2 gets the second and so forth.
You can be towards the bottom (in the "PM" slots) of the list and still be assigned an AM report, as long as you have 8 hours in between work.