And at one point the list produces a subtotal of "24510 years, 3 months, and 3 1/2 days" for the 23 kings of the first dynasty of Kish, so the durations are hardly meant to be just some vague large number.

Note that the odd precision is due to just a single entry. Remove that entry, and pretty much all of the old entries are either perfect squares or nicely round numbers in their numeral system.