diff --git a/app/Service/ServiceTrait/Api/OrderTrait.php b/app/Service/ServiceTrait/Api/OrderTrait.php
index 4866f31..622656a 100644
--- a/app/Service/ServiceTrait/Api/OrderTrait.php
+++ b/app/Service/ServiceTrait/Api/OrderTrait.php
@@ -362,7 +362,7 @@ trait OrderTrait
             $orderMaxPrice = max(array_column($this->orderRes['good'],'price'));
             $this->orderRes['coupon']['amount'] = match ($this->orderRes['coupon']['coupon_type']) {
                 CouponCode::COUPON_TYPE_INSTANT_REDUCTION => $this->orderRes['coupon']['amount'],
-                CouponCode::COUPON_TYPE_DISCOUNT => bcmul(bcdiv("100", bcsub("100",(string)$this->orderRes['coupon']['ratio'],2),2),(string)$orderMaxPrice,2),
+                CouponCode::COUPON_TYPE_DISCOUNT => bcmul(bcdiv((string)$this->orderRes['coupon']['ratio'],"100",2),(string)$orderMaxPrice,2),
                 default => 0
             };
         }