The stations are not divided into categories only because of their footfall, various other features like facilities, amenities, type of city and infrastructure is also taken into account. NZB is an A category station that's officially sure, but I still doubt about the footfall data on your mentioned website to be exactly precise. The govt websites are usually not updated for months and years. I travel between NZB-SC very often, even a few times a week. The station is crowded like hell. Hence I doubt the station could have only around 10k footfall.