Originally Posted by
miamigrad
I believe it comes from E. I'm not certain that you can check for it - it might be that only AA can see that.
This is correct. E is a hidden and internal inventory bucket. A good rule of thumb is that if Y is less than 6 or 7, E is most likely 0. This policy is less generous than DL's, where any open seat is available for "same-day confirmed."