Close as I can get, it seems to store the last digit somewhere else, like in flash, and then write that somewhere else once it reachs a value, probably to save on eeprom writes. Eeproms typically have a 100k write lifecycle, having it write only once every 10 miles takes the lifescycle to about a million miles.
Screwed with it several ways and its always a little off, goes from 80085 to like 80089. or something.
