To add to the info Klayfish provided...
If you are looking for a 4th FP (or booking initially) the tier one FP always show up on top. So if there's a Pandora FP, it will be listed first.
Magic Kingdom is the hardest, imo, because there's no tiers and so many attractions. When they come up, the rides available come up in alphabetical order, followed by the unavailable rides in alphabetical order. If you're looking for 7DMT or Space Mountain, you have to scroll down and look in the "S" section. So rather than just hitting a new time to refresh, refresh, refresh... you have to refresh, scroll down, scroll up, refresh.