1080i on a 720p tv? How is this happening

So I use my device in my bedroom (720p) and on my main tv (1080p) in the living room as well. Why is the resolution of 1080i showing up on as a usable option on my 720p tv and working? It actually looks better than the 720p @ 60hz. Is it upconverting? Using RGB cables in Bed and HDMI in Living. Thanks to anyone that can give me some insight on this.

all 720p tv’s seem to run at 1080 interlaced mode, what is best will be decided by your own eyes and stick to the one you choose,

  this thread will give you some reading on it.

Many thanks for your response. I don’t understand whey they advertise it as a 720p tv yet it supports 1080i as I’m seeing and being told by the set when I hit my display button. That other forum helped a bit but your response was right on. Thank you again.