I just booked TUS-DEN-DCA flights on .bomb, and tried to use KVS to maximize upgrade opportunity - both flights showed NF availability. But after upgrade for DEN-DCA (UA484) wasn't confirmed I checked KVS again - seems that UA484 shows NF0 if the KVS request is only for DEN-DCA, but the same flight shows NF5 as part of a TUS-DEN-DCA itinerary. This seems strange - any explanations?