Google saturation

site and site+inurl command showing different results

[Digerati]

To check saturation of our listings at Google I've been using the "site:www.mysite.com inurl:www.mysite.com" command.

Today I noticed that the while the above mentioned command was yielding about 1 million pages (of a 500,000 page website!) the "site:www.mysite.com" was yielding only 400,000 pages)

So, three questions:

1. Which is more accurate of the two commands to determine Google saturation?

2. Is there a better command to do this?

3. Why are there 1 mill. results for a website with half the number of pages?