Bike speedometer: 20,000 km

A cold January is not the most likely month for such "anniversaries" but statistics happens:



I bought the BC 500 speedometer in Summer 1995 or so and it has measured kilometers on two continents. If I were riding my bike along a geodesic instead of those small gravitational quantum loops, I could have arrived to the antipole of Pilsen (1000 miles Southeast from New Zealand). But the puzzle is: what will happen with the number above after another kilometer? It will either

1. display 20,000 even though the space for the digit "2" seems somewhat constrained
2. display 19,999: it will be stuck
3. display 0
4. display 0,000
5. display "Error", "infinity", or another special message
6. something else