Lever Kind
What a lever is, distinguished by the only thing the machinery needs to tell apart: what it means to do nothing (§8.2.2, §8.2.3).
SETTING — a quantity the model holds: a capacity, a reorder point, a service rate. It has a current value, applying it twice is the same as applying it once, and doing nothing means writing nothing.
TRANSACTION — a quantity the model does: placing an order, dispatching a shipment. There is no "current order quantity", applying it twice acts twice, and doing nothing means acting with the neutral amount, which is an action rather than an abstention.