<?php
add_action('wp_db_backup_completed', array('WPDBBackupLog', 'wp_db_backup_completed'), 11);

class WPDBBackupLog {

    public static function wp_db_backup_completed(&$args) {

        $options = get_option('wp_db_backup_backups');
        $newoptions = array();
        foreach ($options as $option) {
            if ($option['filename'] == $args[0]) {
                $option['destination'] =  $args[4];
                $newoptions[] = $option;
            }
            else{
                $newoptions[] = $option;
            }
        }
        
        update_option('wp_db_backup_backups', $newoptions);
    }

}