Images resize to 640p

I’ve just started building my site and noticed an image I uploaded to Sample Page was automatically resized down to 640p. After doing some digging through the theme files, I noticed the following in the functions file:

function plush_content_width()
{
$GLOBALS[‘content_width’] = apply_filters( ‘plush_content_width’, 640 );
}

I’m not sure why such a small max width would be imposed when the theme is designed to hold much larger content. I’m using a child theme – what do I need to insert in my child theme to override this in the parent theme?

The page I need help with: [log in to see the link]