In Customizing, you can activate this function for document flow at item level. If the item category of the sub-item is not relevant for billing and/or the cost price, then the costs from the sub-items in the delivery are added to the costs of the main item.
The sub-items may have arisen as a result of a batch split, from the expansion of KMATS or from free goods.
You maintain the settings for transfer of costs to the main item in the document flow in field 'Cumulate cost price'. "Maintain copying control delivery document to billing document".