There's no way 300 million people watched this, especially if that number is representing every Netflix subscriber. The largest claimed live broadcast across all platforms is last year's Super Bowl with 202 million unique viewers for at least part of it, but that includes CBS, Nickelodeon, and Univision, not just streaming audiences. Its average viewers for the whole game was 123 million, which is second all-time to the Apollo 11 moon landing.
