Setting up your costs
What happens when I delete a cost rule?
The rule is removed and the gap it would leave is repaired: the rule that came before it is reopened to cover the days the deleted one owned. Without that repair, deleting a rate would leave a stretch of days with no rule at all, and the cost would silently become zero from that date forward.
Deleting the very first rule of a chain repairs nothing on purpose. Pulling its successor backwards would price old orders with a value that was never effective then, which is exactly the history rewriting the effective-dating rule exists to prevent.
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