Why is my site name showing after post title in google?

Can someone tell me how to remove my blog title from my post title in google? For example, if I have a post titled “50 logo design tips”, I want the title to read just that. Currently my posts are showing like this: “50 logo design tips | my site name”.

I am using the popular seo plugin “all in one seo” which has an option to chose how titles are displayed. I have it set to: %post_title%. So shouldn’t this only display my post title? It doesn’t make since.

If this matters…my permalink structure is set to: /%postname%/