Condition contract with Fixed Amount for sales

HI,

Rebate is to give the same per Invoice as a Fixed amount e.g. 190 SAR per Invoice which has to be given at month-end.

Example: There are 10 Invoices created for a Customer in the Export process and irrespective of the value of the Invoices, the business will give a rebate of 190 SAR for each invoice.

So the Credit Note which is to be created at the month-end will be 190 SAR*10 = 1900 SAR.

But the system settled down only 190 SAR but not picked 1900 SAR. what is the solution?