This section will tell you how to see the report of the unpaid invoices and bills. Basically, the report will give you information about how long customer have owed you, in the invoice aging section. And also how long you have owed your supplier in the bill aging section.
To see these two reports, you can go to Debt menu and click more menu then choose either invoice aging or bill aging
The 'Sent' column tells you the ow of a customer but not overdue. 10 day means the customer owned you about 10 days. So does 20 days, and more than 20 days.