Php 在WooCommerce中处理客户总支出中的退款

From Get the customer's total spend for a period of 1 year in WooCommerce answer to my previous question:

// Utility function: Get customer orders total amount from specific status on a period
function get_orders_sum_amount_for( $user_id, $period = '1 year', $status = 'completed' ) {
    global $wpdb;
    return $wpdb->get_var( $wpdb->prepare( "
        SELECT SUM(total_amount)
        FROM {$wpdb->prefix}wc_orders
        WHERE status = %s
        AND customer_id = %d
        AND date_created_gmt >= %s
    ", 'wc-'.$status, $user_id, date('Y-m-d H:i:s', strtotime('-'.$period) ) ) );
}
add_shortcode('user_year_total_spent', 'get_user_year_total_spent');
function get_user_year_total_spent( $atts ) {
    extract( shortcode_atts( array(
        'user_id' => get_current_user_id(),
    ), $atts, 'user_year_total_spent' ) );

    if( ! $user_id ) return;

    $total_spent = get_orders_sum_amount_for( $user_id ); // Get total spent amount

    if( $total_spent >= 1200 ) {
        $text = __('Congrats you are now tier 3.', 'woocommerce');
    } elseif ( $total_spent >= 600 ) {
        $text = __('Congrats you are now tier 2.', 'woocommerce');
    } else {
        $text = __('Congrats you are now tier 1.', 'woocommerce');
    }
    return sprintf(__('Total Amount Spent: %s. %s', 'woocommerce'), wc_price($total_spent), $text);
}

// SHORTCODE USAGE: [user_year_total_spent]

它接收所有完成的用户订单在一段时间内的总支出.

但我面临的事实是，如果订单部分退回，那么总支出不会减少部分退款的金额.

示例: 订购3件T恤 * 10欧盟. 总支出30欧元.交付费用不包括在总支出中. 此外，该订单中的买方退回了1件T恤 * 10欧元.管理员手动发放了部分退款. 订单状态"已完成"，2件T恤 * 20欧盟.但总支出仍为30欧元.

如何从总支出中提取exclude a partial manual refund？