My new 16gb iPhone 5s' storage doesn't equal 16gb?

I bought a 16GB iPhone 5s and when i go to Settings > General > Usage, it says i used 2.3 GB and i have 10.6 GB available. And that would equal 12.9 GB. Shouldn't it equal 16GB?

When the phone comes a little bit of space is already taken by programs already on the phone. All the rest of the space you can put your own things on it.

There are probably other stuff you didn't noticed taking up other things.

As far as it not taking up 16GB, iOS takes up part of it.

Its standard procedure on most, if not all hard drives with OSs on them.