The boarding order process is completely obtuse to me. Other than platinum and concierge getting first dibs (obviously) it seems somewhat random. Last trip (Fantasy) we chose 10:30 boarding, but because of long check-in lines we didn't check in until ~ 11:15. We got group 13. This last time (Dream), we selected the 11am boarding time (earliest available), got there by 10:30 and checked in by 11:00 almost on the dot. We got group 7.
:shrug:
This is how I understand it:
Firstly, it's not a boarding time that you select it's a Port Arrival Time. Your actual boarding number is tied to your PAT.
Now, as you know, there are 15 minute windows that you select for your PAT. Each window has X number of boarding numbers assigned to it. Just for the purpose of this discussion, let's say each PAT window has 5 boarding numbers assigned to it.
I've read two different explanations as to how the specific boarding number is issued within each window:
1) it's assigned based on when you completed your online check in.
2) it's assigned based on first come, first served within your boarding window.
When you arrive at the port, regardless of how it relates to your PAT, you will receive the same boarding number that you would receive if you arrive at your correct PAT. So, I take that to mean that #1 is the more likely procedure for assigning boarding numbers.
It's possible for 2 parties traveling together, with the same PAT, to have different boarding numbers.
Even with 10:30 terminal opening/PAT windows, actual boarding does not begin until 11:15-11:30 for most cruises. Concierge goes first (usually boarding number #1, but not announced as such). Then Platinum (#2). Then they start announcing boarding numbers roughly every 5-10 minutes, depending on how quickly the line is moving.
It's quite likely that a 10:30 PAT could result in a #7 boarding number one cruise and a #13 on a different cruise. That part (how many actual numbers are within each window) I don't know. Maybe it varies based on the sizes of the various parties selecting that PAT?