All games are tracked badly especially when digital putchases are thrown in to the mix, people just like/dislike the guestimates used based in how it sits personally for them.
To be more blunt
sony fan: tlou has sold 3mill+
ms fan: tlou has sold 2.1mill (sales va shipped, digital added on etc)
nintendo fan: just wait till nintendo get around to releasing our systems sellers... youll see..
sony fan: mario sucks
ms fan: mario sucks
nintendo fan: mario rocks
sony fan: halo is so lame, whats it on now? 7?
ms fan: halo is the bomb, bring me more
nintendo fan: you wouldnt know a good game if it fathered you
and so the arguments continue until the ends of time.