public function register_meta() {

		register_meta(
			'post',
			'_llms_length',
			array(
				'object_subtype'    => 'course',
				'sanitize_callback' => 'sanitize_text_field',
				'auth_callback'     => array( $this, 'meta_auth_callback' ),
				'type'              => 'string',
				'single'            => true,
				'show_in_rest'      => true,
			)
		);

	}