A6 Speedometer
 

So my speedo has this weird feature, it graduates in 10s all the way up to 80kmh with a mark between each 20 kmh i.e. 0 I 20 I 40 I 60 I 80 I I 100
But between 80-100 there are two graduations. What the actual?...

Anyone know why or for that matter the value of the double graduations (can't be 5 or 10 kmh each)