It doesn't matter how you "view" the number (hex, binary, or decimal), the value is still the same. So, adding one is the same, whether you add one "in hex" ($01) or "in binary" (%00000001) or "in decimal" (1). You still just have "a number".

One thing that might help clarify this for you is to use the Calculator in Windows (if you're using Windows). Using the "Scientific View" (View >> Scientific), type in a number, then change the radio buttons to Hex, or Bin, or Dec. The VALUE hasn't changed, just the way it's represented.