Multi instance

Here, I am creating a process for purchasing goods, starting from the request until the goods are placed in the warehouse. There is a case where the requested goods are shipped partially, for example, 1000 units are purchased, and they are delivered in batches of 300, 300, and then 400. How can the goods that are shipped partially (the input of the shipped goods is in the packing list) have instances that are related to their parent instance, but they can still proceed to the task of "update inventory gudang"for the partially shipped goods?
purchasing.bpmn (92.6 KB)

So, when we are at the “packing list” task, we input the quantity that is being shipped. If the shipped quantity matches the purchased quantity, the process will continue to the end. However, if the quantity shipped is partial, it will create a new instance in the “packing list” and later be merged again before the “stock opname” process.