You can ask your TA to check this for you. But if you did your on-line check-in, you selected a port arrival time during that process. The only reasons I know that you don't need to pick a time is if you are concierge, Platinum (I think), or you booked cruise, hotel, flight, and transfers through Disney. If you are any of the above, you didn't need to pick an arrival time because you get the earliest boarding numbers.