- Model version
- 1.0
The formula, in words
- Free time comes off first, and it is a threshold rather than a discount. A container returned inside it costs nothing, and the first chargeable day is the day after it ends.
- The tariff is a ladder, so cost does not track time. Each tier applies only to the days inside it, which is why a container held a quarter longer than another can cost two thirds more.
- The count and the proof are separate. Every figure here can be computed from four numbers, and none of them can be tested without a document, which is the difference between a claim that is right and a claim that can be read.
where d is the chargeable days and h the days held.
where C is the container cost, i the chargeable day index, and ri the rate for that day at its tier.
A worked example
Free time 7 days, so a container held 19 days has 12 chargeable days, being days 8 to 19. Days 8 to 14 are seven days at $95, which is $665. Days 15 to 19 are five days at $145, which is $725. That container is $1,390.
The check. 49 chargeable days across six containers, and 39 days sat inside free time and cost nothing. The tariff line is $0 at day 7, $665 at day 14, $1,680 at day 21 and $3,570 at day 30, so the ladder is not linear and a container held a third longer than another does not cost a third more: container 4 was held 26% longer than containers 1 and 2 and cost 66% more.
The line that changes no total. Container 6 adds $0 to the claim and is the second thing a reviewer notices, because a claim carrying a line worth nothing invites the question of what else is in it that was not checked. Removing it moves the total not at all and removes a challenge, which is the cleanest demonstration on the page that the packet and the arithmetic are separate problems.
What this does not model
Entitlement of any kind, the contract that would decide it, notice, liability, mitigation, whether the hold was anyone's fault, currency and exchange, interest, set-off, limitation, the terminal's own charges, and every question a reviewer would ask that is not one of the twelve in the reviewer script. This page models five things a reviewer reads for. A reviewer reads for more than five things.