AO will first select the default bin of the location on the transaction. When you open the location screen, and select the Bins tab, the bin checked Default is the bin the inventory will be placed in. However, AO looks to see if the Item has an assigned default location/bin, if so, then it will use the item's assigned bin. Be aware that although you assign a bin/location to an item, if you are using a different location than what was assigned, then it will use the location's default bin. The only other way to override the default bin is by manually assigning the bin in the transaction.