Qm is for Minimum Quantity
Q is Quantity
Qt is the total quantity of an item regardless of the expiration or location.
Qm is an optional trigger for adding items to the Cart List. If enabled, when the Qt of an item drops below the Qm for that item, it is added to the Cart List 1:1.
Optionally, under Settings tab> Settings and Options there is a button "Retroactive Qm" that will go through your entire inventory and add every item where Qm > Qt to your Cart List.