clocks

Quick question is the mileage kept/recorded on the ECU or is it the Speedo/Clocks. Reason I ask is, seen a few speedo's for sale, and they say they're not sure of the mileage, but surely the mileage should be recored on the bike(ECU). Otherwise someone could get a set of very low mileage...

Can anyone help my 07 690's clocks started flickering on sunday and said "dat 1.1 and something else ...... 3.2 cant remember but it was another 3 letter word. They stopped working after that, the unit lights up but theres no info and the rev counter doesnt move. This bike is breaking my heart!!!