Pressplay Custom Header size

I can’t get the custom header sized correctly to prevent it from tiling. I’ve tried the standard 121 x 990 size, as well as 1263 x 121, which is the size I got by inspecting the element with a right click.

What gives with this issue? Why doesn’t Pressplay give the size in its custom header page, instead of making us guess?

Here’s my blog so you can see what I’m talking about:
https://www.rahmakrambo.com/