Sales Analysis income totals not tying to totals from Postings

Hello,

We're just finishing up our first season using Tessitura, and our Finance Director has realized that the income shown in the Sales Analysis for a performance does not tie to the income calculated by adding the posting totals together for the same performance. Any ideas why this would be the case? 

Thanks!

Kathleen

(Since I'm not sure if this is a ticketing or a finance forum question, I'm going to post it in both places.)