When a kit is purchased on the same order as one of it's components Trunk does not seem to pull the quantity of the component unit from inventory.
For example if on order 001 a person orders 3 units of widget y, and orders 1 kit x which is made up of 1 widget y and 1 widget z. Trunk will correctly subtract 1 widget z from inventory, but not subtract 1 widget y from inventory.