In the Webmaster tool of Google one query shows that the avg. position of my site is 6.6. However, when I do the search, I could not find my site within 400. Does this mean that my site is in "Sandbox"? How can Google shows the 6.6 avg. position? Is this the actual position if the site is not in "Sandbox"?
Google webmaster tool does not shows real time rankings, it is historical rankings and may defer from current search position.
One more thing; Google ranking will be different from country to country; for example search result in Google.com US, and Google.com UK will also give different result.
In your case; difference is very huge and it is to early to say that your website is in sandbox without reviewing the keyword and your website.