There isn't a trial for it so it mostly sales.
Strong start for PUBG sales on Xbox - Leaderboard showing 500K players 24hrs after launch #VGN— THE RED DRAGON (@TWTHEREDDRAGON) December 13, 2017
I was rank 430k earlier today in NA and Wooden was 50k in Europe so the 500k number seems legit.
Also an Xbox insider said it's selling well.
PUBG is selling extremely well on Xbox.— Jez (@JezCorden) December 14, 2017
Game has problems but its crazy fun so I'm glad to see it succeed on console.