I talked to some friends while away on vacation, one of them owner of a 2009Honda Jazz (Fit for the US). He observed the same thing but there is a very good explanation after all.
The car, if you do not do extensive mileage every day, will stay in counting days left to service.
However (and this applies to my past month mileage) if you do more than a 150 km a day (roughly 100 miles) the computer will switch to km left to service as this is more accurate and convenient than counting days backwards.
What is more, this "detail" was clearly stated in my friend's (also owner of a 2009 I2) manual but it is absent in mine. In addition to this, my I2 "rich" edition came with headlights' sprinklers but were absent from my friends' also "rich edition" bought just a month before mine. And to make things worse, my headlights automatically adjust to the road but my friend's car you have to do it manually using the up and down cursor left from the steering collumn.
What on earth?
Someone said that some of the I2 cars sold in Greece are the model sold also in Germany, some are just a plainer model...

