I was very confused on my FSS display, as a week ago it displayed the wrench and the number 14. Several days later it showed 11, and on the day I took it in for service it read 9. I asked if their was something wrong with the FSS as I know I had driven over 5 miles in a week. The service rep said that it was set to read in days when the mileage was low! (25,600) I notice it now is set to distance.
You might also consider changing coolant at the same time as you do brakes.
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E