Sounds about right to me. My previous laptop had a resolution of 1280x800. This one has a resolution of 1366x768, but the intended resolution that you set your game to is not decided by the resolution of your laptop/monitor. You are making the game for other people no? Most people have 1080p monitors these days so it's best to use the standard HD resolutions @ 640x480 (480p), 1280x720 (720p) & 1920x1080 (1080p). The game I'm working on is 1080p, it pretty much scales down perfectly to my 1366x768 laptop screen (I mostly test on my laptop because I can't be bothered switching my secondary hd monitor over as my primary screen each time I want to test something, unless it's vital I need to see it in its actual resolution).
P.S: don't forget that you can always draw in the black bars yourself & add them into an interface.