If you want to eat early on Select Dining just be there when it opens and you should have no issues.
In a different post you mentioned that you are looking at booking aqua class. If you do that, you do not have a table in the main dining room, your dining room will be blu, which is all open seating. The app and website make it look like you can choose dining options (Select, Early, Late) in blue but you can’t. Blu is all open seating with no reservations so if you want to eat early, you just show up early.