Just off yesterday and I feel the boarding situation is a mess.
We had earliest arrival time of 10:30 for both my cabin and Dsis cabin.
We dropped Dsis and BIL off at around 10am to the front line (didn't know anything about a third floor!!). They were taken care of by porter right away with all our luggage and got in a very short line to show Id and then enter terminal. They moved to check in right away in the Castaway line. They picked up a card from a man standing near the lines. When they checked in my Dsis asked what is up with getting this card (boarding #8) I thought it was linked to our checkin time online and WE did arrive at our time. The CMe said they are still trying to work this out as people are coming early and messing things up (her words). Anyways she looked in the system somehow and saw that they had Boarding #4. Took her boarding number 8 crossed it out, wrote 4 and then initialed it.
So my DH and I drop off car and return to terminal about 10:45 and get in line. Goes pretty smoothly. We get to the guy with the cards and get 18

My BIL comes up to us and says they got 4. So when we checked in the CM checking us in gave us all our cards and stuff and said "do you have a boarding number yet". We said yes # 18, but also asked and said, hey we are here in our time slot why should we board at 18? He said what number does your family have? We said 4, he took a small card out and gave us #4. He didn't even look at our ressie and was happy to do it.
SO I have NO IDEA how they assign numbers. They are doing it randomly and are trying to be accomodating to people and quite honestly doing it as they go.
BUT THE BIG ISSUE..... Getting into the ship when your number is called.
That was a complete and total mess. Not a good way to start your cruise. I can't believe Disney who is known around the world for the best way of Cueing people in a line, can't have a STINKING LINE FOR BOARDING (yes I am yelling). People were pushing and irritable and didn't know what number was called. IF the local deli can have a "now serving number" sign I gotta believe Disney can do this
I will be writing the customer service address about this. It was horrible. Make a line like Southwest and have boarding number lines so people can start getting in line. Ridiculous. My DH just about went nuts on a man pushing me and his wife yelling about getting through (they were two numbers earlier). It was ugly.
Sorry, getting off my soap box!