Minimum time until next appointment

Hi,

We are using Appointment+ on our website for scheduling demos. https://skyprep.com/schedule-a-demo

We would like to set a minimum time before a demo/appointment can be scheduled. For example, we'd like to have at least 1 hour to prepare for a demo so we don't want a demo/appointment scheduled for a time slot that is less than 1 hour in the future.
For example, if it is 1:20pm right now, a person would not be able to schedule a demo for today at 2:00pm. They would be able to schedule it for 3pm (if that time slot is available).

How do we achieve this? In the settings page, I've set "Appointments lower limit (hours)" to 1 hour but this does not seem to make that work.

Is this possible?