I am a CP traveling from CLT to PHX next Saturday. I could see from the seatmap that the 320 equipment shows 6 available seats. I called the CP line and asked how many were available for upgrade so that I could decide whether or not to use miles to upgrade. I was suprised to find out that no seats were currently available in the O availablility class.

I thought that generally speaking 2 seats were held back for purchase. I can even see 4 seats, but 6?

I don't have much experience with US on the East side. Is 6 of 16 held back normal? thx for the info.