Unscrambling the Online Marketing Statistics

I like the numbers to work out. So I tried this exercise. Here are some real numbers from one of my websites.  Any ideas on why this stats don't make sense.

UnScramble
Take the term unscramble.

When you type "Unscramble" into Google, my site is 10th. I'm only looking at organic rankings and traffic in this article).
When I look at my analytics traffic over the last 30 days, I see that I have received 2,072 visitors who arrived using some search term containing  the word "unscramble".
When I look at the Google Adwords tool to get a sense of the traffic on this term in the last 30 days, it reports 301,000 searches.  So, it appears that I got around 0.7% of the traffic.  This makes some sense to me. I'm 10th and get less than 1%....could be true.


Sound-alikes.  My site is first or second for this term (Meaning: Same sounding English words but with different meanings and spellings).
Analytics reports 18 visitors whereas Adwords reports 3,600 searches for the past 30 days. So 0.5% came to my site.  This does not make sense to me. I'm the first or second term, how come I'm getting less than 1% of the searches.

I think the first example makes some sense but the second one doesn't. I would think that as the first, second, or third in the rankings, a site should harvest between 4-25% of  the searches.  Unfortunately, I have far more examples where the numbers don't make sense than where they do.  Any ideas? Anybody have any experience trying to reconcile different pieces of Google-based data?

One possibility is that that the adwords tool is showing not just the searches but all the  impressions that would be created if an advertisement was created to be run against the word Unscramble.