As ever, the steveg site seems to explain it best:

Check out the "this weeks rankings" page, and at the top it tells you which events have just beenadded to the computer (Hamburg, Zagreb, GB F8....), and which will go on at the end of the week (Portschach, Greece F3, ItalyF14....), so we need to look forward to Drew's top 10 Brits list next Monday.

Here's the link. I wonder how much the ATP pays Steve G, whoever he is!

http://stevegtennis.com/rankings/2006/s052206.htm