Keep hidden and apply on reaching

Hide time fare until min mileage is reached, add to meter on reaching it.

You choose it from the Min mileage handling screen, reached from the time-handling row of fare rules .

The four options for the time charge before the included mileage is reached

This is set per fare, so a day rate and an airport flat rate can handle it differently.

Once the included mileage has been driven, the time charge is added to the meter as it comes, whichever option you pick.

Add to meter instantly — Add time fare to meter instantly regardless of reaching the min mileage.
Take from min mileage — Deduct the equivalent amount of time fare from min mileage left.
Throw away — Until min mileage is reached throw the time charge away.