Animal Crossing: New Horizons sold 11.77 million copies in 12 days, making it the "best start ever" for a Nintendo Switch title. "about 50%" of players located across Japan, America, and Europe bought the game digitally. AC:NH sits at 13.41 million copies sold to date.

Nintendo had expected these sales numbers for total lifetime sales, not the first 6 weeks.
Another tidbit, the highest selling game on the Switch is Mario Kart 8 Deluxe at 24.77 million copies sold to date.
Source//Original Article: https://www.nintendolife.com/news/2020/05/animal_crossing_new_horizons_has_already_exceeded_nintendos_lifetime_sales_predictions