It's not that they put it on a spindle that runs anti clockwise and turns it back, the electronic odometers have their memory in a computer chip. That chip is accessed electronically and it's memory is replaced by programming into a new number.
To open a meter the needle may have to be removed but that doesn't mean that it will give an error of 10 to 20 Km p h when fitted again. If it sits on zero correctly it will display speed correctly as before, provided that the tyres are not exceptionally large or small.
This is particularly true for the corolla mentioned above that does not have a stop pin at zero. Its needle rests at a pivot in its internal mechanism and is very easy to reinstall.
