Originally posted by born sleepy:
maybe the system has changed since the booklet was printed? it also says all CO upgrades are capacity-controlled, though I'm not exactly sure what that means.
This system is new as of early November when CO went to EUA processing.
Capacity controlled essentially means that CO holds back some seats for last-minute full-fare purchases, rather than make them all available for upgrades. If still unsold, you can grab those at the gate.