The clean items waiting to be put away form a stock: a quantity counted at a particular time. Newly dry items add to it; items put away remove from it. Those additions and removals are flows, measured over an interval.

For a simple count: ending stock = starting stock + additions − removals. Use matching units and account for every relevant route in or out. Items per day cannot be added directly to an item count without specifying the number of days.

The bathtub is another useful example: litres stored, litres entering per minute and litres leaving per minute. These quantities obey an exact accounting relationship; a metaphor such as a “stock of trust” does not provide the same measurement automatically.