Appointments+ question about a setup if possible

I'm using the Appointments+ plugin and have set up a car service booking with one car to start, but 3 available bookings within that car. For the bookings page, I want to show the service - from 3 different city to city then the customer chooses a day and time. Right now I have it set up so there are two dummy providers and one main provider to account for 3 seats in the car. The service when booked lasts 4 hours but I want to be able to give the customer the ability to choose any time they'd like that isn't already booked. So if I put the service at 4 hours though it only shows options at every 4th hour where I'd like to show options at every 30 minutes unless there is a 4-hour time slot booked. Is this possible