When you turn on the 2.35 aspect ratio marker setting in the A6300. Look at where the line is on the LCD screen. Next put your eye up to the eyehole and you'll see that the lines are in a completely different area. In the LCD, its so much tighter and I suspect its completely incorrect.
This has been an issue since release and supposedly the March 3rd 2017 firmware update for the a6500 fixed the same issue on that model. But us a6300 users only using a camera one model year older, still havent gotten an update for this crucial video issue!