A message “when delivery type is free shipping, basic delivery fee and conditional free shipping fee are 0 won” is returned. What should I do?

The message comes when you enter basic delivery fee and conditional free shipping fee after selecting a free shipping. Please enter 0 for deliveryCharge and freeShipOverAmount..

<Three delivery fees>
- Initial shipping fee on return (deliveryChargeOnReturn) : Delivery fee charged to a customer which was originally paid by a seller for a free shipping 
- Return fee (returnCharge) : One-way fee paid for return delivery 
- Delivery fee (deliveryCharge) : The fee that a customer has to pay for conditional free shipping 

* Note
All the 3 fees are one-way fee. You need to set a delivery fee according to the right delivery fee condition. Therefore, you have to set 2 delivery fees depending on the type of delivery fee.

<Setting free delivery>
- Enter initial shipping fee on return and return fee.
- Make sure to enter 0 won for basic delivery fee and conditional free delivery fee. 
- The delivery fee charged to a customer for a return is "initial shipping fee on return+return fee". 

<Setting paid delivery >
- Enter basic delivery fee and return fee amount. 
- You have to set 0 for initial shipping fee on return and conditional free shipping fee. 
- The delivery fee charged to a customer who returns a product is "basic delivery fee+return fee" 

<Example of paid delivery>

deliveryChargeType: "NOT_FREE",
deliveryCharge: 2500,
freeShipOverAmount: 0,
deliveryChargeOnReturn:0,
returnCharge:2500

deliveryChargeType: "CONDITIONAL_FREE",
deliveryCharge: 2500,
freeShipOverAmount: 10000,
deliveryChargeOnReturn:0,
returnCharge:2500