I haven't heard that there's a formula that they always follow. The Passporter suggests that it's often based on the ages of the guests in your party with similar ages in the same rotation and that "On the first night you'll find more kids in Animator's Palate, families in Parrot Cay, and adults in Lumiere's/Tritons."
You can request early or late seating and which rotation you get but it's not guaranteed.
We had late seating and enjoyed it since we didn't need to rush back to the ship in St. Maarten. It didn't matter in St. Thomas since onboard was 4:30.