Change Excerpt Length on Home Page

I’m looking to modify the excerpt length in the blog section of the parallax home page. I’ve edited the return count in the sketch-functions.php of my child theme, but this seemed to have no effect. And I’ve checked that the folder hierarchy in my child theme directory matches that of the parent theme. Thoughts?

Here is the code I modified:

function invert_lite_excerpt_length($length) {
return 20;
}
add_filter(‘excerpt_length’, ‘invert_lite_excerpt_length’);