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.