That is why there are multiple stages to the sensors on each axle, so the system can auto-correct the algorithm based on actual pad sensor signals. Up until that last trigger, the estimate was based on how many times you applied the brakes, and how hard you applied them. Not surprising that can be off.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue