Did you just add your site? i think you're weight goes up after a week. I have a site that has 370 pages indexed in google, no pagerank and my weight is a little over 5,000
Site is full of supplemental pages, I doubt the Google API sees them so that is why you have low weight
I have a script that uses the API to make a search something like http://www.wwwsearchsolutions.com/google.php