http://www.pcgamer.com/playerunknowns-battlegrounds-has-sold-over-10-million-copies/

Since launching into Early Access on March 23, 2017, PlayerUnknown's Battlegrounds has sold over ten million copies. That's ten million copies in just 165 days—which is an average of over 60,606 copies sold per day. Not bad for an unfinished game that began life as a mod.  

In that time, PUBG has also eclipsed both CS:GO and Dota 2 in Steam player count, and its runaway success has prompted other online stalwarts to craft their own variations of the hugely popular formula. In case you were wondering, GTA Online's PUBG-style mode is not as good as PUBG.