Thanks for the update Mauricio.

The Discount transaction is essentially an 'applied detail' to the paid invoice. If you select the 'Include Applied Detail' option for the Customer Transaction report, this effectively removes Discount transactions from the 'main' list and moves it as strictly an applied detail printing underneath the invoice.

I was not able to duplicate an issue with the report total being different (with your version or 80B), depending on whether or not this 'applied detail' option is selected. So if indeed something is not working correctly for you as it should be, we'll need to know all of the options you are selecting - in case some combination of options is the culprit.