The second season of Netflix's "Stranger Things" averaged 8.8 million viewers in the first three days of its release. Each of the nine episodes were watched by more than 3 million of those in the 18-to-49 demographic coveted by advertisers, according to Nielsen.

The first episode, titled "Chapter One," averaged 15.8 million viewers in that same three-day period (the second season dropped on Oct. 27). All nine episodes were watched by 361,000 people after the first 24 hours.

Nielsen also found that over the first three days, the average number of episodes watched by those in the 18-49 demo were 2.9.

• "Chapter Two" averaged 13.7 million viewers and 9.6 million people 18-49 viewing over the first three days of its availability.
• "Chapter Three" averaged 11.6 million viewers and 8.1 million viewers 18-49 viewing over the first three days of its availability.
• "Chapter Four" averaged 9.3 million viewers and 6.6 million viewers 18-49 viewing over the first three days of its availability.
• "Chapter Five" averaged 8 million viewers and 5.6 million viewers 18-49 viewing over the first three days of its availability.
• "Chapter Six" averaged 6.4 million viewers and 4.5 million viewers 18-49 viewing over the first three days of its availability.
• "Chapter Seven" averaged 5.3 million viewers and 3.7 million viewers 18-49 viewing over the first three days of its availability.
• "Chapter Eight" averaged 4.9 million viewers and 3.4 million viewers 18-49 viewing over the first three days of its availability.
• "Chapter Nine" averaged 4.6 million viewers and 3.2 million viewers 18-49 viewing over the first three days of its availability.

In comparison, the Season 8 premiere of "The Walking Dead" on AMC earlier this month averaged 15 million total viewers and 8.8 million among adults 18-49 in the three days after it aired.

Nielsen began more fully measuring Netflix content earlier this month.

Netflix said then that Nielsen's numbers were wrong. It repeated that on the subject of "Stanger Things."

"Their math might be from the upside down," a Netflix spokesman said in a statement. ("The Upside Down" is an alternate dimension on the show.) "Nielsen only measures a fraction of our members' viewing. For example, they don't measure mobile viewing. Our series are global and member viewing patterns vary greatly (what device they watch on, where they're watching, what they are watching), making it very difficult to model, even if they had accurate samples."

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CORRECTION: An earlier version of this article inaccurately said the entire second season of "Stranger Things 2" averaged 4 million viewers per minute in the three days after it debuted. While each episode averaged over 4 million viewers in the three-day period, the season as a whole averaged 8.8 million viewers.