Isn't it possible that some of the same viewers watched more than once?
The official word: AMC’s “The Walking Dead” is the first cable series in television history to reign as the biggest show of the fall season among Adult 18-49 rating, beating all broadcast and cable entertainment series including “The Voice,” “Modern Family,” “X Factor,” “Two and a Half Men,” “The Big Bang Theory” and “Grey’s Anatomy.” Last night, the 9PM premiere of “The Walking Dead’s” mid-season finale delivered 10.5 million viewers. The series encored at 10PM and then again at midnight, delivering an additional 3.6 million & 1.1 million viewers respectively, totaling 15.2 million viewers for the night. With Live plus 7, “The Walking Dead” adds another 3.4 million viewers a week on average. “The Walking Dead” Season 3 to date reigns as the number one ad supported drama series in basic cable history among total viewers, adults 18-49, adults 25-54, adults 18-34, men 18-49, men 25-54 and men 18-34. AMC resumes the final eight episodes of “The Walking Dead” season three on Sunday, February 10th at 9pm EST.
In addition, the season three mid-season finale of “Talking Dead” at 11pm attracted 2.2 million viewers. The live after show, hosted by Chris Hardwick, expands to a one-hour program on Sunday, February 10th at 10pm EST immediately following “The Walking Dead.” Embassy Row’s Michael Davies and Jen Patton serve as executive producers and Brandon Monk is co-executive producer.