[Biturbos4] How does the 'service in xxxx miles' work ?

[Bill Coleman]

A couple months ago my S4 popped up the 'service in 600 miles' message.
I've driven it over 1000 miles since then and now it says 'service in 500
miles'.  My wife's A4 started up with 'service in 1200' miles last weekend,
and in a matter of days it's gone to 'service in 500 miles'.

Most of my driving is on the highway with a 60 mile round trip to work and
back.  My my wife is mostly city driving, and relatively short trips.  I
assume that's the difference, but has there every been a discussion of how
the miles to service is computed?

I searched the AudiWorld archives and found out I'm not alone - some people
have seen the miles to service number go up!  There are also a number of
suggestions that it's a bug in the software.

Bill
00 S4 6sp
01 A4 Avant 1.8tq sport 5sp (wife's car)
87 Porsche 928S4 5sp (the 'other' S4)