The account number is both the shipper and the billing account
In a UPS setup your account number does two jobs at once: it states who created the shipment and which account the invoice is billed to. So for businesses working with more than one UPS account, which number you enter has a direct effect on cost. Take it from the shipper account number on your UPS contract.
If the service code field is left empty, the standard service is used. If you work with express or a different service level you have to state the code explicitly; otherwise your shipments are created at a service level you did not expect, and the price difference surfaces later.