The travel time for shuttle buses indicated in the system is approximate, because the transfer by shuttle means presence of other passengers. This is why the pick up time and the passengers list is calculated and managed by the carrier company. On top of it, the travel time of shuttles depends on the number of stops.
For future for more comfort we advise you to book an individual transfer. In this case the car will arrive exactly at the time you indicated.
The detailed information concerning the transfer service by shuttle and private transfer service you can find following the link below: