Why does the UPS tracking number need 30 digits?

Here’s the tracking number for a shipment I have in process. (I changed a few digits so don’t bother to look it up.) “420144689074892108381211337129”.
Why do they need so many digits? I understand they need check digits to avoid errors. Usually 5 are plenty. That leaves 25 for useful information. If every person on the planet had a unique number that would only take 9 digits. If each person shipped a package every day for 100 years and every package had a unique number that would only take 15 digits. Is the time (to the nearest hundredth of a second) and address (to the nearest 100 meters) in there?

What the heck are they recording or trying to prove?