Fixing size of largest photo in Header Highlight content

Hi, The header highlight content section displays the name of the post next to its featured image. The first photo & name displayed in the grid is double-sized. Its image should have the same aspect ratio as for all the other posts, however in reality the image does not fill the available space. I think it is displaying the helena-slider image instead. How do I make it so that the largest image is displayed with the same aspect ratio as the other images in this section? If you need an example, see www.banno.me. Thanks.