How does prosite get to know file space used?

Hi Guys!

Hope everything is going great and you are creating state of the art plugins like you always do

I have a small question if you can help me out. I am trying to build a wp-admin end dashboard area (that displays on the /wp-admin main page when you login). It lists the Blog title, Username , firstname , The level of the user (interms of Prosites) AND how much disk space has been used by him from his allotted quota.

There is a setting in prosites where you can set a limit on how much disk space is allowed for a particular level. Hence there must be a function or a check somewhere to see how much of this has been used.

I want to use that check (call the function) and display how much of it has been used in the admin dashboard area that I am creating.

If you signup on edublogs, you can see that area in the dashboard that displayes this information. I want something like that which is almost complete. Just need this final piece on info.

Many Thanks!
Keep up the good work!