Threaded Comment Numbering in Genesis. https://sridharkatakam.com/threaded-comment-numbering-genesis/

functions.php

// Change 'genesis_html5_comment_callback' to 'gtcn_basic_callback' provided by Greg's Threaded Comment Numbering plugin for numbering commnets
add_filter( 'genesis_comment_list_args', 'sk_add_numbered_comments' );
function sk_add_numbered_comments( $defaults ) {

	if ( function_exists( 'gtcn_basic_callback' ) ) {
		$defaults['callback'] = genesis_html5() ? 'gtcn_basic_callback' : 'genesis_comment_callback';
	}

	return $defaults;

}

style.css

.commentnumber {
	float: right;
	font-size: 12px;
	background: #ddd;
	padding: 5px 10px;
}