[Plugin: Google Analytics for WordPress] GA installed on main domain instead fo subdomain

Hi all
From my main domain http://www.mydomain.com I created a subdomain http://subdomain.mydomain.com
On this subdomain I installed Google Analytics for WP but if I go to check in the Google Adwords CP where I run the adwords campaign for the subdomain, the Analytics code is shown as “residing” on mydomain.com and not on the subdomain itself, as I expected.
Is this correct? and how can I make sure the code is installed within the right page?
thanks
Fabio

http://wordpress.org/extend/plugins/google-analytics-for-wordpress/