Disable additional thumbnail and custom image size?

Kleo adds its own thumbnails (678px) (in addition to WordPress thumbnails) and a custom image size (1138px). This unnecessarily bloats our upload directory (we work with many screenshots) because Kleo adds additional files for each screenshot. Where are these image sizes actually used?

I disabled these sizes now by adding the below code to functions.php in the child theme which appears to solve the problem. (We use 600px thumbnails). What I would like to know is if this can cause problems.

function kleo_child_setup() {
set_post_thumbnail_size( 600, 9999 );
remove_image_size(‘kleo-full-width’);
}
add_action( ‘after_setup_theme’, ‘kleo_child_setup’, 11 );