I have already found out how to delete my series recording. I no longer schedule series recordings because it doesn't work. When I set up a series recording for new episodes only, it records all airings new and old. It also records the airings on multiple channels of the same network. In other words if I schedule a show on HD channel 1014 WWJ-CBS it records the same show from channel 15 and 233 as well, so now I have 3 copies of the show's episode. This is a similar problem that you have when trying to mark channels as my favorites. It adds all the channels for that network of which some networks have 3 channels.
The bigger issue hear is when are these 2 problems going to be fixed. I'm a new customer to Xfinity and right now I'm not sure I made the right choice. These are important issues to the customer and need to be remedied. Are they going to be fixed? Seems I remember Comcast had this 'marking favorite channels' problem a long time ago and apparently was never fixed up to this point.