The reason we are starting to count at zero is because we are saying "How many cells beyond the first cell", If we are already on the first cell, then we are 0 cells beyond the first cell, so the first cell is cell 0.
This is why we start at zero for things like positions, but we don't start at zero for the widths and the heights. We already are at the first cell, and we need to know how many cells to move to go to where we want. When we actually want to first cell, we move 'zero' spaces.
