Rear brake pads

[checkm8]

I have two questions related my 2008 3.0si.



Situation: current mileage – 57,500. Front pad replaced at 43,668, rear pad replaced at 48,046


At 50,000 miles service indicator said – 37,000 miles left on front pads, 13,000 miles left on rear
At 57,500 service indicator says – 21,000 miles left on front pads, 3600 miles left on rear


My driving is mainly in city, stop and go, so I understand the quick drop. My questions are:
1. Why is rear dropping much faster than front?
2. In the inspection report last month (at 57,000) brake pads were measured at – Front: 11mm Rear: 9mm. Could service indicator be faulty?


thanks in advance.