This includes used sales, but not pirated copies.
GamesIndustry.biz said:Now, Dying Light has entertained more than 8 million players - a figure that clearly delights Techland CEO Pawel Marchewka, even if it doesn't quite surprise him. "We were counting on big numbers, because Dead Island was pretty popular," he says when we meet at Digital Dragons. "Dying Light is just so much the better game. We would have been surprised if it did worse than that."
Source: http://www.gamesindustry.biz/articles/2016-08-04-techland-dead-risingThe fact that Dying Light reached 8 million players, Marchewka says, is a result of such choices. "That doesn't include illegal players," he adds, though it does include second-hand sales.