functions.php

<?php

/**
 * Shared Counts - Change "Total" to "Shares"
 * @author Bill Erickson
 * @see https://www.billerickson.net/code/shared-counts-change-label-for-total-field
 */
function ea_shared_counts_change_total_label( $link ) {

	$classes = explode( ' ', $link[ 'class' ] );
	if( 'included_total' == $link[ 'type' ] && in_array( 'style-icon', $classes ) ) {
		$link[ 'label' ] = _n( 'Share', 'Shares', $link[ 'count' ] );
	}

	return $link;
}
add_filter( 'shared_counts_link', 'ea_shared_counts_change_total_label' );