I always try to sit in 26 and never have had my choice unavailable. I think I remember reading somewhere that meals are allocated amongst zones in J, so each FA has a certain amount of chicken/beef/pasta. Then if one is used up in a zone, they can go back and reallocate from another zone that didn't use all of a particular choice. Not sure of the validity of that, but seems like a good way of doing things with such a large cabin.