This may be a dumb question. I picked up a XBR55X900e yesterday. My first 4K set coming for an eight year old plasma. Why am I not getting the full 55” when viewing HD or 4K movies and shows? Is there a serring I’m not seeing? Even when watching 4:3 it doesn’t stretch to the top and bottom of the screen. Wide mode is set to “normal”. I’m using a 4K Firestick if that helps. Maybe a setting in there? Thanks for any help.