customer summary: how comes the "expense" field?

[Yu Liansu]

Hello.

Customer Summary lists profit and expense of each customer. I know 
gnucash must have calculated customer from invoices, but how does it 
know the expense of each customer? The expense are transactions 
involving expense accounts, some of them linked to Bills, so I can 
imagine gnucash have enough information to give a "supplier & service 
provider summary" with expense column, but how does it associate expense 
with customers?

In my customer report, all customers have an expense of "0", except one 
with 9443.00.

Thanks in advance!

-- 
Yu Liansu, web professional.

http://www.yuliansu.com