Every time a Car in Top Drives races it gets closer to needing to be serviced, each car has 10 Races before it needs to be fully serviced, however after each time a Car Races a timer starts so if you wait a period of time the Car will gain one of its servicing points back, meaning you can race again quickly and not have to wait a long time for all 10 points of servicing to come back to race.

For example:

I race my Honda CRX VTEC, going from 10 Race on the Service Counter down to 9, a Timer starts for 4 minutes (Displayed on the Card in the Garage), after this 4 minutes is up the Honda will be back to the full 10 Races available.

However if I race a further 9 times knocking the Service Counter to 0, I now have the option of waiting the few minutes for the 1 point on the Service Counter to race, paying Gold for the full 10 Races or waiting a longer period of time for more than 1 Race point to restore.