Tolerance rules for voucher match

Hi all,

Quick question: when defining tolerance rules for type 1 (voucher match) you can add rules for quantity, cost and amount. In the case of a 3-way-match how are these used?

For amount, it's clear: if you have 5% tolerance and you try to voucher 6% more than the amount received, you get the error.

For the quantity, I don't see how this is used - you can't voucher more than was received so when is this rule applied?

How can one change the unit cost at voucher match, I don't see a way to modify this on the screen? So I'm not clear how this is checked against the tolerance - if at all?