Does anyone even listen to creationists these days?

[Sigurd]

Perhaps they counted by tens.

Well.. sort of. It's a mix between our system and Roman like numerals.
They use letters from their alphabet and they have letters for 1 - 9, 10 - 90, 100 - 400 where 400 is the largest number with a single letter. 500 would be 400 + 100