I think, well thought, I know what this means on the "Event Sales Report" and the "Show Sales Report", but I would like clarification so that the next a promoter or tour company manager freaks out when there is a negative number on their reports, I can confidently explain why this is.  I understand that when they exchange a ticket from one event to another that the reports would show a negative for the first and a positive for another, but what does it mean when the two come to a negative number?