They are the cost of sales for individual line items, calculated based on average cost at time of sale. These are the amounts debited to the Inventory - cost account.
All I can say is that it does not. It was designed and coded that way. Your fixation on this behavior suggests you would be better off using accrual basis accounting. As you may know, it is actually illegal in some jurisdictions to use cash basis accounting when inventory is involved. There are just too many shortcomings and compromises. Manager is, at heart, an accrual basis accounting system with modifications for cash basis reporting. But the cash basis performance was and is an afterthought.
I assumed as much. You still haven’t shown the necessary information to diagnose what is going on with invoice 4615. I’ve asked more than once. But you seem more focused on an issue I cannot do anything about and unwilling to examine what could actually be causing your problem.
I’ve offered all the advice I can. Good luck finding the error.