No no no. What I'm thinking is that you see the 2.8 - 6.3 is the maximum aperture (or rather, smallest f-stop number) that the lens can go from a certain range.
i.e. when a lens is 70-300, f/2.8~6.3, it means that maximum aperture at 70mm will be 2.8, and at 300mm will be 6.3.
But anyways, f/8 and f/22 - f/22 will definitely give you a lot more DOF, but more often than not this is not discernible or evident if you're shooting landscapes - more evident when you're shooting stuff like macro.