protected function get_chart_data() {
		return array(
			'type'   => 'amount', // Type of field.
			'key'    => 'amount', // Key of result field to add when counting.
			'header' => array(
				'id'    => 'sold',
				'label' => __( 'Net Sales', 'lifterlms' ),
				'type'  => 'number',
			),
		);
	}