"3.4 million copies had been sold by the month of June 2017 – of which, 915,000 were digital" - https://en.wikipedia.org/wiki/Horizon_Zero_Dawn#Sales
The information was released early June, the figure given is for April 30th. Even follow the link to the source on wikipedia, at no point in the cited article does it say "as of june" it doesn't give a date.
A good example of that is the break down of sales for PS4’s Horizon Zero Dawn. As of April 30, more than 3.4 million copies of the game have been sold. Of those 915,000 were digital sales, according to PlayStation.
Predictions (Made July 2019)
LTD: PS4 - 130m, Switch - 110m, XBO - 52m 2019 : PS4 - 15m, Switch - 18.8m, XBO - 4.8m 2020: Switch - 22m (Peak Year)