The Upside Down delivered upside for Netflix in the third quarter: “Stranger Things” season 3 was the most-watched season of the series to date, according to the streamer.

In the first four weeks of release, “Stranger Things” season 3 was watched by 64 million member households, Netflix said in the Q3 letter to shareholders. The company previously boasted that 40.7 million accounts watched the show in the first four days of its July 4 debut, marking its biggest-ever audience for a movie or TV series in a four-day window.

What’s important to note: The data isn’t independently verifiable. Moreover, Netflix records a “view” of a series if a member account watches just one episode to at least 70% completion.

Still, according to measurement and ratings firm Nielsen, “Stranger Things 3” is the most-watched Netflix original it has analyzed over past two years — at least, over the initial four days of release. From July 4th to 7th, the show had an average minute audience of 12.8 million viewers and reached 26.4 million unique viewers in the U.S., Nielsen reported. Episode 1 of S3 drew an average minute audience of 19.2 million viewers over the four-day period, a 7% bump from the season 2 premiere episode for the comparable period. There are caveats, too, with the Nielsen numbers: These are only for the U.S. and they measure only viewing on connected TVs (excluding computers and mobile devices).

Netflix last month renewed “Stranger Things” for season 4, and series creators and showrunners Matt Duffer and Ross Duffer signed a multiyear overall deal with the streamer to create films and television series

In the Duffer Brothers’ “Stranger Things” season 3, set in 1985 in Hawkins, Ind., the crew of Eleven (Millie Bobby Brown), Mike (Finn Wolfhard), Lucas (Caleb McLaughlin), Max (Sadie Sink), Will (Noah Schnapp) and Dustin (Gaten Matarazzo) are back together again over the summer — and there’s a new mall in town. But tensions grow as they enter teenage and the evil monsters from the Upside Down make a terrifying return.

“Stranger Things 3” also stars David Harbour as Chief Jim Hopper, Winona Ryder as Joyce Byers, Priah Ferguson as Erica Sinclair, Maya Hawke as Robin. The series is executive produced by the Duffer Brothers, Shawn Levy and Dan Cohen of 21 Laps and Iain Paterson.

Also in its earnings announcement, Netflix called out viewership numbers for other shows:

  • “Secret Obsession,” starring Brenda Song, was watched by 40 million households in the first four weeks
  • Limited drama series “Unbelievable” was watched by 32 million member households in its first 28 days
  • “Otherhood,” directed by Cindy Chupack in her feature directorial debut, was watched by 29 million households in its first four weeks
  • “Tall Girl,” a YA drama starring Ava Michelle, was viewed by 41 million households in the first 28 days
  • Season 3 of “La Casa de Papel” (“Money Heist”) became the most-watched show on Netflix across non-English language territories with 44 million households watching the new season in the first four weeks of release.