Google Query Stats Questions - what does it mean?

I just lucked into the most fabulous opportunity - the SES Exhibit Hall in Miami featured a well-staffed google both and not that many visitors. I got Vanessa Fox's full attention for an hour. (If only I had been better prepared with questions - what an opportunity!!!)

I need to revisit this question about Top Search Queries.... What does it mean?

It's explained as: "Top search queries are the queries on the selected search property that most often returned pages from your site" ...over the previous three weeks.

Does this mean that:

a. These are the searches that my site ranks highest on. - I don't think so since I know there are searches where I am number one but which are not listed. Those are lower volume searches.

b. These are the highest volumes searches that returned my site in the results. If this is true, what is the cut-off that google is using to say that my site was "returned"? My table has seaches where the highest average position is 11.

I thought b. was the answer but Vanessa said that this couldn't be the whole story since she has seen tables where people are listed with positions as low as the 40s.

I've now thought of a third possible explanation...

c these are the highest volume searches where some minimum number of people actually clicked on my link.

This is the only explanation that I can think of that can explain this table.
This would require Google to:
1 - Find searches that people have clicked on my site
2 - Prioritize them by volume

Explanation C also makes sense because its using similiar data to whats in the second table but in a different way. I will test this by picking some huge volume term such as "learning games" or "homeschool" (where I place around 40th) and click on them and see if these terms hit the table. Stay tuned....

I'm also puzzling now over the term: "selected search properties". What does this peculiar phrase mean?

My blog with most of the notes from the conversation -http://learn-to-market-online116.blogspot.com/2006/07/vanessa-fox-at-ses-miami-google.html and my site http://www.Time4Learning.com

PS - my next personal project is to figure out how to use trackbacks on blogs and some other basics about blogging. I just sent this in to a newsgroup and google has let it go up: I'm also going to put it up on David Naylor's blog, is that too many?