There are times in life when things are rather subjective or can change from time to time, one such scenario could be while dining. The waiter reaches over your salad with their pepper grinder hovering and says, "Just Say When" implying you tell them when to stop grinding pepper on top of your salad.
In contrast, when injecting a mold with resin there is a set volume the mold can accept.
Overfilling or underfilling the mold can have impacts on part quality, production performance, and the health of the molding operation, let alone lowering profits and wasting money.