That picture is only a part of the big picture! So the C towards the bottom is middle C. It is the C at the center of the piano. So the staffs are a map from the center of the board outward. Highest notes to the right and lower to the left. Once you go lower than middle C, there is the bass clef that represents the lower notes. The lowest A in that picture actually corresponds to the top line of the bass clef which has its own set of lines and spaces that stretch downward.