Operations, Inventory and External Items
Operations are functions within your organisation that gerenally have an hourly rate or cost. Different employees or machines are typical "operations" that are charged out at different hourly rate. For example "Employee Group A" might be charged out at $100 per hour so would be set up here as an item of "Employee Group A" at a value of "100".
Inventory Items are generally items or functions that are always sold at a fixed price. The value in this case is the unit cost.
External Items are costs that vary depending on what a particular supply may charge for a particular job. In this case the value would be set at "1" and the total amount charged by the external supplyer would be entered against a job when known.
All the values entered here should be before margin and before tax.