PAT is the time you should arrive at port. If you arrive early, you will likely be asked to wait. If you arrive late, they will still let you in. Boarding group is the group number that you board the ship. Once boarding starts, they call BGs in order. Boarding groups are usually called about 5-10 minutes apart, though sometimes longer (two weeks ago on the Treasure BG 4 took like 20 minutes for some reason, and of course we were BG 5, lol).