Normal is a broad question but that is well below what it probably could/should be. What type of movie and how were you watching it,streaming, on SD card, internal memory, format? A lot may depend on your update status and what else is going on while you're watching it.
I'd also ask what brightness setting were you using as well as what app did you use to play the movie.
I get around 4.5-5 hours with 65% brightness playing 720P streams via Kodi on my Surface 3 so an average avi stored internally should yield far more than you are getting