[Plugin: WordPress SEO by Yoast] Problem with add title

Hello
I want to add a text to all of my post title ( for example “Hello”)
I went to (/wp-admin/admin.php?page=wpseo_titles#top#post_types)
SEO–> Title and Meta –> posts = then I put
%%title%% - Hello but hello text does’t add to all of post title!
I run “Twenty Ten” theme
what I should to to for solve this problem?

http://wordpress.org/extend/plugins/wordpress-seo/