Field help (CPNOPE)

If you do not need this component to be readily available at the start of the production process, use this field to define the specific operation or stage in the manufacturing process at which this component must be available to it. Holding back availability of this component until it is needed can be particularly beneficial in some circumstances. For example, for cost savings if this component is an expensive purchased product or storage costs are expensive, for saving on warehouse floor space if it has a large volume or for catering for specific characteristics such as a cooling period. 

This becomes the default operation number and can be changed for an order if necessary.

 The routing operation is referred to as the weighing 'phase' within the Weighing functionality (if you use the Weighing module).