Understand how promotion discounts are applied to multi-level items

Promotional discounts can be applied proportionally to multi-level items.

For a multi-level configured item, promotion discounts must be applied proportionally across the root and all of the sub-items in the hierarchy.

In Commerce, order level discounts are applied proportionally across all items in the order (unless an item is specifically excluded from benefiting from such a discount). For a configured item, a proportional discount must be applied to all items in the configuration hierarchy. For example if an order level promotion applies a 10% discount then that 10% discount must be applied to any configured item in the order.

For a multi-level configured item, however, the promotion discount must be applied proportionally across the root and all of the sub-items in the hierarchy. This applies only to configured items that are not sold as a package (i.e. where the soldAsPackage value on the root item = FALSE).