I am trying to get all the id's in my WordPress navigation and convert it to a string so that I can use it in my wp_query to get the pages that are only listed in the nav. Here is how I am getting my id's

$menu_name = 'primary';

 if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $menu_name ] ))    {
$menu = wp_get_nav_menu_object( $locations[ $menu_name ] );
$menu_items = wp_get_nav_menu_items($menu->term_id);
 }

 foreach ( $menu_items as $menu_item ) {
 $numbers[] = $menu_item->ID;
}

 $number = implode(',',$numbers);

What I am finding is that the code is returning the wrong numbers. When I go to the admin area and hover my mouse over the pages, the number that shows up in the address bar on the bottom of the screen doesn't match. What am I doing wrong?