TotalBeginner
The calculations are dynamic in that the ground handlers have to start running calculations even before the aircraft is loaded so they know where and how much cargo can be placed onboard. This has to be tied in with how many passengers and where they are seated. The numbers are run many times in the course of loading a aircraft prior to departure. Many operators build a tolerance into the numbers to allow for last minute adjustments by the flight crew without rerunning all the numbers.
You can’t just load the aircraft and hope the numbers will be within limits.