Example of how to add additional registration counts to to the event publish metabox

add_all_regs_to_event_metabox.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file
add_action('AHEE__Events_Admin_Page___generate_publish_box_extra_content__event_editor_overview_add', 'tw_ee_add_total_reg_count_to_event_publish_metabox', 20, 1);
function tw_ee_add_total_reg_count_to_event_publish_metabox( $cpt_model_obj ) {

    //Sanity check to confirm we have an EE event object.
    if( !$cpt_model_obj instanceof EE_Event ) {
        return;
    }

    $view_all_reg_link = EEH_HTML::link(
        add_query_arg(
            array(
                'route'       => 'default',
                //'_reg_status' => EEM_Registration::status_id_cancelled,
                'event_id'    => $cpt_model_obj->ID(),
            ),
            REG_ADMIN_URL
        ),
        esc_html__('View All Registrations', 'event_espresso'),
        esc_html__('View all registrations for this event', 'event_espresso')
    );

    $view_all_link_html = EEH_HTML::span(
        '',
        '',
        'dashicons dashicons-groups ee-icon-size-20'
    );
    $view_all_link_html .= ' ' . $view_all_reg_link . ' : ';
    $view_all_link_html .= $cpt_model_obj->count_related(
        'Registration',
        array(
            array(
                'REG_deleted' => 0,
                //'STS_ID'      => EEM_Registration::status_id_cancelled,
            ),
        )
    );

    echo EEH_HTML::div(
        $view_all_link_html,
        '',
        'misc-pub-section'
    );
}

add_cancelled_regs_to_event_metabox.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file
add_action('AHEE__Events_Admin_Page___generate_publish_box_extra_content__event_editor_overview_add', 'tw_ee_add_cancelled_reg_count_to_event_publish_metabox', 10, 1);
function tw_ee_add_cancelled_reg_count_to_event_publish_metabox( $cpt_model_obj ) {
    
    //Sanity check to confirm we have an EE event object.
    if( !$cpt_model_obj instanceof EE_Event ) {
        return;
    }

    $view_cancelled_reg_link = EEH_HTML::link(
        add_query_arg(
            array(
                'route'       => 'default',
                '_reg_status' => EEM_Registration::status_id_cancelled,
                'event_id'    => $cpt_model_obj->ID(),
            ),
            REG_ADMIN_URL
        ),
        esc_html__('Cancelled Registrations', 'event_espresso'),
        esc_html__('View cancelled registrations for this event', 'event_espresso')
    );

    $view_cancelled_link_html = EEH_HTML::span(
        '',
        '',
        'dashicons dashicons-groups ee-icon-color-ee-grey ee-icon-size-20'
    );
    $view_cancelled_link_html .= ' ' . $view_cancelled_reg_link . ' : ';
    $view_cancelled_link_html .= $cpt_model_obj->count_related(
        'Registration',
        array(
            array(
                'REG_deleted' => 0,
                'STS_ID'      => EEM_Registration::status_id_cancelled,
            ),
        )
    );
    
    echo EEH_HTML::div(
        $view_cancelled_link_html,
        '',
        'misc-pub-section'
    );
}