PHILADELPHIA–(BUSINESS WIRE)–During the week of September 12 – September 18, Comcast customers watched 57 million hours of content on Xfinity On Demand. TV was the most-watched category, representing 25 million (44 percent) of the total hours viewed. The top 20 TV episodes on Xfinity On Demand that premiered during this week were:       Rank Movement Series Network 1 – American Horror Story: Roanoke (Premiere) FX 2 – Power (ep 9) STARZ 3 – The Case of: JonBenet Ramsey (Part 1) CBS 4 – South P