Hi, Ron, 
If quantity invoiced is negative, it usually means that receipt was over-invoiced previously (quantity invoiced > quantity received), either by manual increase of quantity during matching, or in consequence of inspection in receipt (one of return for credit, return for rework or scrap for credit actions).
To be sure, you should check all invoices matched with selected receipt (in Invoiced Purchase Order window) and transaction history for that receipt (inventory or non-inventory transaction history window).

@Adam Bereda You are very helpful aways. thank you.

currently our user in posting proposal , invoice 14733 , there is nothing match could be found. see attached.

we do have an auto job will do the auto receipt matching, so i believe this job did the adjustment for those negative transactions.

i believe there could be some goods still in inspection, or simply need do receipt so that the user could do matching again.

Thank you.

OK, if matching is done by job, most probably reason is inspection and not manual invoiced quantity change. 
You may check receipt itself, to see received quantity and inspection results, and see invoices matched with this receipt in Invoiced Purchase Orders

@Adam Bereda I will follow your advice. Thank you.