Regarding safety stock, which statement is not correct?

Safety stock can be calculated by a supply plan $-$ based on how many days of anticipated need you want to have on hand.

Instead of having the plan calculate safety stock $-$ an item can be assigned a fixed safety stock quantity for the duration of the plan, or a safety stock quantity that varies over the duration of the plan.

Whether it's calculated or user$-$defined, safety stock is always considered during a supply plan run.

Safety stock can be calculated by the supply plan $-$ by anticipating future needs and applying service level percentages to determine time$-$varying safety stock levels.