Hi: USD 70.00 W/M is our buying and you informed us on 25 August the selling was USD 80.00 W/M. So on our invoice we debited you 80.00 W/M and give you credit 5.00 W/M for profit (80.00 less 70.00 = 10.00 for us to mutually share 50/50 which means 5.00 W/M for each of us). Therefore an amended invoice is not needed. I hope this explanation helps. Thanks and speak soon.