public function get_chart_legend() {
		$legend = array();

		$total_discount_query = array(
			'data'         => array(
				'discount_amount' => array(
					'type'            => 'order_item_meta',
					'order_item_type' => 'coupon',
					'function'        => 'SUM',
					'name'            => 'discount_amount',
				),
			),
			'where'        => array(
				array(
					'key'      => 'order_item_type',
					'value'    => 'coupon',
					'operator' => '=',
				),
			),
			'query_type'   => 'get_var',
			'filter_range' => true,
			'order_types'  => wc_get_order_types( 'order-count' ),
		);

		$total_coupons_query = array(
			'data'         => array(
				'order_item_id' => array(
					'type'            => 'order_item',
					'order_item_type' => 'coupon',
					'function'        => 'COUNT',
					'name'            => 'order_coupon_count',
				),
			),
			'where'        => array(
				array(
					'key'      => 'order_item_type',
					'value'    => 'coupon',
					'operator' => '=',
				),
			),
			'query_type'   => 'get_var',
			'filter_range' => true,
			'order_types'  => wc_get_order_types( 'order-count' ),
		);

		if ( ! empty( $this->coupon_codes ) ) {
			$coupon_code_query = array(
				'type'     => 'order_item',
				'key'      => 'order_item_name',
				'value'    => $this->coupon_codes,
				'operator' => 'IN',
			);

			$total_discount_query['where'][] = $coupon_code_query;
			$total_coupons_query['where'][]  = $coupon_code_query;
		}

		$total_discount = $this->get_order_report_data( $total_discount_query );
		$total_coupons  = absint( $this->get_order_report_data( $total_coupons_query ) );

		$legend[] = array(
			/* translators: %s: discount amount */
			'title'            => sprintf( __( '%s discounts in total', 'woocommerce' ), '<strong>' . wc_price( $total_discount ) . '</strong>' ),
			'color'            => $this->chart_colours['discount_amount'],
			'highlight_series' => 1,
		);

		$legend[] = array(
			/* translators: %s: coupons amount */
			'title'            => sprintf( __( '%s coupons used in total', 'woocommerce' ), '<strong>' . $total_coupons . '</strong>' ),
			'color'            => $this->chart_colours['coupon_count'],
			'highlight_series' => 0,
		);

		return $legend;
	}