If you are using a GS7, I assume you are on Marshmallow and your device uses "adaptive brightness" as opposed to the old auto brightness.
You essentially set your limits by wherever the brightness slider is set and with adaptive brightness enabled, it gives you a range slightly above and below where your slider is set. So if you move the slider to the right you will have a range that includes a higher maximum brightness, and if you move it farther left, your max brightness will be at a dimmer level.