NEW YORK: The fantasy favorite “Game of Thrones,” the most popular series in HBO’s history, returned for its sixth season with what may or may not be the show’s most-watched episode ever.

It all depends on which Nielsen company measurement you look at. HBO’s experience is a vivid illustration of how new ways of watching television are imposing difficulties on people whose job it is to pin down how many people actually experience something.

Nielsen estimated that 7.94 million people watched “Game of Thrones” at 9 p.m. EDT Sunday, when the episode first aired. That would make it the third most-popular episode of the series ever, behind the season five finale (8.11 million) and the first episode of last season (8 million).

Add in people who watched the show’s first two repeats, along with those who streamed the episode within 24 hours, and viewership jumps to 10.7 million, HBO said. Because of the growing popularity of streaming, that number eclipses a similar count for last season’s finale (10.3 million).