Which mileage counter? Not much information, but I think I know what you mean. You're most likely talking about your next task. This can happen if there is hidden instructions in the scenario, sometimes used to display messages or trigger something. As soon as you pass them the mileage counter gets updated. Can also happen if you run over a red signal in a standard scenario with your path not yet set by the dispatcher. It can then be impossible to complete the scenario. Finally a bad scenario can also be the reason (wrong final destination set).
Sometimes the mileage does not count down if you are a long way away from the destination/task you are to perform. As Torf states it usually has to do with how the scenario has been put together.
The distance is not a matter, it is hidden instructions mostly. You can see the distance when you press F1, the blue marker shows the mileage to the waypoint you select in the left window.
Torf Good point - I explained that badly but it only seems to occur when you are a fair way from your destination - and it suddenly appears when you get closer - so I put 2 +2 together and got 5!!
