Insulation work is an actual measurement. It is an open end PO.
Cost will be summarized as the work done.
What site approved is quantity have been verified.
Purchaser have a responsibility to checked correctness what contractor
submitted with the unit rate and issued the PO to cover the claim.
Idea to split PO into original / add work , I have no objection.
Im , may I lost the update PO , sent me the latest one.