What do the coordinates returned by querying pic\_crop mean when related to a profile picture. I have tried working this one out by cannot figure it!

Please help!

The values for left, top, right and bottom are a decimal like e.g. left 0.20115. What does 0.20115 mean? If you look at the source code for a facebook profile you will see that facebook is using a percentage to offset the profile photo. How does 0.20115 translate to facebook source of style="left:-23.13%;"