We can't add that easily in SAMP, as making such a timer and updating it every second requires updates to be sent to the player every time you want to change the timer, so, if you want to display milliseconds, you'd need to send an update every ms, to every player in the race. This would probably use a lot of resources and cause lag, if you're receiving updates at such rates. Even when we only do it every second, I don't think it's a good idea.