How does “What the row tells you” work on the Customers page?

Invoices, invoiced and outstanding are the group totals, in the reporting currency, and the footer totals them for the page. Xero orgs is how many of the group's organisations have billed the customer — a two or more is a customer the group bills from more than one company, which is exactly what a single Xero cannot show. Last invoice orders the list by default, so the customers the group is working with now are at the top. Where: Customers (/accounts/customers).