Read more post excerpt

Blogpost page is setup with post excerpt and they work fine.
Problem is with a post with less words then the lenght set in the option: Post Excerpt Length

For example: the option is set to 40.
With a post with less words then 40, let’s say 10, the Continue reading button is visible. This should not happen because the option is set to 40.

Why is this button visible on these posts? Can’t seem to find it, and it looks awfull!