How can I set discounted_price of shipping_lines correctly?

Retired Boards Appdev Graphql Basics And Troubleshooting
1

When I creating the order, I have included the param “shipping_lines” like this:

{
  "shipping_lines": [
    {
      "title": "Free Shipping",
      "custom": true,
      "discounted_price": "0.00",
      "discounted_price_set": {
        "shop_money": {
          "amount": "0.00",
          "currency_code": "SGD"
        },
        "presentment_money": {
          "amount": "0.00",
          "currency_code": "SGD"
        }
      },
      "price": "5.00",
      "price_set": {
        "shop_money": {
          "amount": "5.00",
          "currency_code": "SGD"
        },
        "presentment_money": {
          "amount": "5.00",
          "currency_code": "SGD"
        }
      }
    }
  ]
}

But the order I created got shippling_lines like this:

{
  "shipping_lines": [
    {
      "id": 3510226256012,
      "carrier_identifier": null,
      "code": "Free Shipping",
      "delivery_category": null,
      "discounted_price": "5.00",
      "discounted_price_set": {
        "shop_money": {
          "amount": "5.00",
          "currency_code": "SGD"
        },
        "presentment_money": {
          "amount": "5.00",
          "currency_code": "SGD"
        }
      },
      "phone": null,
      "price": "5.00",
      "price_set": {
        "shop_money": {
          "amount": "5.00",
          "currency_code": "SGD"
        },
        "presentment_money": {
          "amount": "5.00",
          "currency_code": "SGD"
        }
      },
      "requested_fulfillment_service_id": null,
      "source": null,
      "title": "Free Shipping",
      "tax_lines": [

      ],
      "discount_allocations": [

      ]
    }
  ]
}

The discounted_price turns to “5.00” automatically, is my understanding wrong? or my param is wrong?

Can anyone help me about this?

Thank you very much