hi mark your car as an e.c.u. (brain ) once your original clock was taken from your car and another clock fitted, ( your dads ) the cars e.c.u. stores the mileage hence when your dads clock was fitted, the e.c.u. will remember the mileage and display it on that clock. if you would fit a new clock to your car it will still remember the original mileage. this is deigned to avoid tampering with the mileage .
ian
August 2009