SEO credit for subdomain blogs?

[CMSSolutions98]

One of my clients is currently running a webstore through Volusions. They would like to add a blog to their website, but since Volusions doesn't currently support blogs on the same domain we would have to create a Wordpress blog and link it to a subdomain. (http://support.volusion.com/article/linking-your-blog-your-volusion-store) Using this method, will their primary website receive any SEO credit for the content being created on the blog or will it only count towards the subdomain?

Thanks!

[irvingw]

the subdomain is considered a new site. Their main site will only get SEO credit if the subdomain links (like somewhere like in the footer) to the main site