Under these specific circumstances, changing the Mar-te invoice to an earlier date, before any sales of the item were made, would apply the same average cost to all units, both those sold and those remaining in stock. But it is never a good idea to modify accounting data for such purposes. If you were ever to have a question or dispute concerning the Mar-te invoice, your records would be incorrect.
I wonder, however, why this is important to you. Without changing the Mar-te invoice, the Inventory Profit Margin report is correct for the period over which it was defined. You bought and sold units of the product, resulting in a calculated profit for that period of time. The result of the delayed Mar-te invoice is that units remaining in inventory carry a higher average cost. But by the time they are sold (assuming no more purchases), everything will balance out on an Inventory Profit Margin report for the longer time period. The first 30 bottles sold will be at a lower cost, the last 6 at a higher cost. But the profit margin for the longer period will be the same as if the original purchase, plus all customs and transport charges, occurred the same date and all bottles were sold at the same average cost.
All this is the result of using average cost method for valuing inventory. Other approaches are sometimes used in accounting, but average cost is the only one Manager supports.