The Average Cost and/or Last Cost fields are updated from the Purchase Transaction line item Cost, plus the distributed Shipping.
The Shipping is distributed based on the number of units received.
For example, if the Purchase Transaction consists of 90 bath towels and 10 bottles of bath oil, then 90% of the Shipping is distributed to the bath towels and 10% is distributed to the bath oil.
See:
Purchase Manager - Parameters - Update - Distribute Shipping
Purchase Manager - Parameters - Update
Purchase Manager - Parameters
Purchase Manager Contents