Replacing a function in Parent theme not working

I’m trying to replace an add_image_size function to edit the size that it produces but it doesn’t seem to be working.I’m using Catch Box as the parent but it won’t change the featured image size. I did manage to override it through the child, but its still not working.

function my_child_theme_setup() {
    add_image_size( 'featured-slider', 725, 320, true );
}
add_action( 'after_setup_theme', 'my_child_theme_setup', 11 );

It still remains 644 width on the page even though I changed it to 725