Element Not Displaying Correct Width

Hi, I built an author box on one of my sites using the block element. Unfortunately, it seems like the box isn't displaying the correct width, which should be the same as the post width. I have exactly the same box design on another site using GP just with some other info and it is working perfectly, not sure why this is happening. I'll leave the URL to the site below, just scroll down to the bottom of any one of the blog posts to see what I mean.

Thanks.