Selecting which object to align to in Powerpoint 2007

If it is Align Vertically or Horizontaly, it puts both objects in the middle of delta between them. If it is Left or Top or values like that, it uses the X-most value to align the other object(s). So if you have a shape that is one inch from the top and another that is 5 inches from the top, it will align the 5-inch one to the 1-inch (the "Top Most").