Time of booking matters in upgrade priority.(Assuming fare class and status are the same, as they are here.)

Are you saying that there are for seats were five seats left for upgrades based on the seat map/first class availability or were you checking the V/X availability?

If it was indeed V/X and you didn't clear, when the ticket was booked it may not have had the upgrade requested. There's a DL issue as well that sometime will list it as upgrade eligible as opposed to requested.