How to make the gallery wider. Tiled Gallery Carousel Without JetPack.

Hi, I am using a Twenty Seventeen child theme. WordPress version 5.0.3. I have searched the forum and online and unplugged plugins and cleared the cache but cannot find a solution that works.

I am trying to make the gallery wider. I have found on this forum that the below code works to change the width –

// Changes tiled gallery width

function custom_tiled_gallery_width( $custom_hello_text ) {
return 1200;
}

add_filter( ’tiled_gallery_content_width’,’custom_tiled_gallery_width’);

I am nervous to add this to my functions.php and have instead used the Code Snippets plugin. What happens is odd. When I refresh the gallery page for a split second it is wider but then it goes back to normal.

In the answer I read, someone had the same problem but apparently the problem was due to his server taking too much time initially and was corrected and it worked for them. I have been refreshing my page and clearing the cache for a few days now, so I don’t think that’s the problem.

Any help to increase the gallery width will be much appreciated.