Match Action - Match Dispute

I need to know how this match action is supposed to work. I will appreciate a step by step testing document on same.

I followed below steps at my end to test:

Created a PO with qty 5 and unit price 100

Created receipt by copying from this PO as it is.

Created a Voucher copying from above receipt but modified unit price to 200.

Ran matching.. got exceptions.

Created an adjustment voucher copying from above voucher.

Modified unit price to -100 and saved.

Now ran matching from this voucher page only. The adjustment voucher is in matched status.

But the original voucher is still in exception status.