I've just reserved a Range Rover Sport (XJAN) for our trip to Orlando later this year. Apparently it's a 'guaranteed model' reservation which when I enquired from SIXT means that there's only one car in the category. They didn't say anything about the car being on request so can I assume that this is just a car they have lots of within the fleet in the area?

Reason I ask is that naturally having paid a significant sum for a 2 week rental for this vehicle I would be really disappointed if I turned up and was told they didn't have my 'guaranteed model' car. Any ways to prevent this potentially happening?

Grateful for any advice.