Solid-Stark on 06 January 2015
It means the PS4 slowed down during December. If it's some 1m+ overtracked, then that means XOne beat it or fared much better compared to PS4 during the month worldwide.
e=mc^2
Gaming on: PS4 Pro, Switch, SNES Mini, Wii U, PC (i5-7400, GTX 1060)