How long was it between you checking the two values?
It wouldn't be impossible to pick up that kind of headwind in a relatively short period of time.
The only other thing you need to know is what exactly the display shows, which is somewhere else on here. Just do a search.
I read something similar a while ago, and believe the pax screens show GS (in values the public are familiar with; MPH/KPH) which is taken from the Air Data Computer(s). On BA747's I've travelled on, it also tells you the head/tail wind component, which I found interesting.
Maybe it's simply because Boeing make better airplanes... Or shall we not go down that route...
Hope that helps.