Discounting with discount_amount not working in API

When an order is being created, there are two fields that can be used to issue discounts: discount_percentage and discount_amount. When the discount_percentage field is given a value, ERPNext automatically calculates the discount_amount field and adjusts the total amount based on the discount and if discount_amount is supplied, ERPNext automatically calculates the discount_percentage and adjusts the total amount. So ultimately, the two can be used.

Whenever I send discount_percentage in API, it works as expected as seen below:

But the issue is whenever I use discount_amount, ERPNext seems to be ignoring it:

What could be wrong please?