Twenty Thirteen Banner not appearing "as is"

Hi, I’m using the Twenty Thirteen theme and under Appearances -> Header it says if you upload an image of 1600x230px it will be shown “as is.” I’ve done this and it’s not being shown “as is,” but rather a large part of it is chopped off. I am using a child theme and I thought perhaps I had added CSS to it that was making the banner area smaller and causing the problem but I activated the regular Twenty Thirteen and uploaded the banner image again (and double checked that it is indeed 1600×230 even in the media library) and it’s still being cut off. Here’s the site.