I still have no idea what you mean by "it plays back in HD." I understand what HD is, but you haven't explained how you know what the resolution of the playback is. Neither monitor indicates the pixel dimensions of the rendered image. If you have Zoom Level set to a percentage and you know your computer monitor's display resolution, then you could figure out the resolution that Premiere is rendering at.
And as Shooter has already pointed out, referring to the "canvas" didn't clarify anything for me. I assume that term is used in FCP or Avid, but I have no experience in those NLEs.