HBO - Game of Thrones SPOILERS INSIDE. you have been warned

[Jakensama]

I think it takes into account On Demand and later viewings too - so all the bad press from the Sansa Rape one hurt it, and all the "OMG Best Episode Ever" press from Hardhome probably increased it.

Also, the episode after the rape scene was a holiday weekend which I'm sure hurt ratings a bit too (depending on how long the window for viewership was).