What is the correct process when canceling remaining quantity in a receipt route

We place orders for multiple lots of material ordered by total weight.  A single line will have a weight that is for multiple units that will have significant variances in what weight is delivered for each unit.

An advanced shipping notice (ASN) is sent, and a subset of lots and weights is identified. 

The ASN is then used to receive the weight, and the lots are created through Multi-Location and the lots enter the receipt route

The actual weight will be received, the receipt route activated and a quantity of weight is now available for use.

Later a second ASN is sent with the remainder of the weight ordered.  The weight is then divided into lots and are created each with the appropriate weight.