By default, the time increment for hourly bookings is 1 hour.
On the contrary, by enabling the option Time increment based on duration, the increment will be the same as the booking duration. Therefore, for a two-hour booking, the times shown will be 8:00; 10:00; 12:00; etc.
Moreover, you can also enable the option Time increment including buffer that adds the buffer to the time increment based on duration.
We created a one-hour booking and set the Buffer to 1 hour. We activated both options Time increment based on duration and Time increment including buffer.
The availability will consider both the booking duration (1 hour) and the configured buffer time (1 hour) and will show as below.