admin-columns.php

<?php
add_filter( 'manage_<your_post_type_slug>_posts_columns', 'jet_add_custom_admin_columns' );
add_action( 'manage_<your_post_type_slug>_posts_custom_column', 'jet_render_custom_admin_columns', 10, 2 );

function jet_add_custom_admin_columns( $columns ) {
	$columns['jet_custom_column_1'] = __( 'Column name #1', 'text-domain' );
	$columns['jet_custom_column_2'] = __( 'Column name #2', 'text-domain' );
	return $columns;
}

function jet_render_custom_admin_columns( $column, $post_id ) {

	switch ( $column ) {
		case 'jet_custom_column_1':
			echo get_post_meta( $post_id, 'your_meta_key', true );
			break;

		case 'jet_custom_column_2':
			echo get_post_meta( $post_id, 'your_meta_key', true );
			break;
	}

}