Line numering algorithm in Natural programs

What is the line numering algorithm for Natural programs ? I see that algorithm changes when lines is more or less, but what are the ranges when it changes ?

It would have been better to post this in the Natural News and General Topics forum.

A module with 1 to 999 lines is numbered by 10.
A module with 1,000 to 1,999 lines is numbered by 5.
A module with 2,000 to 4,999 lines is numbered by 2.
A module with 5,000 to 9,999 lines is numbered by 1.