Calendar Event Booking Form – Number of tickets bug

I have created a booking form for events using the Event Calendar. The event has a limit of booking 2 places, which can be achieved. However, once this maximum has been reached, the booking for will not allow me to edit this number downwards (say back to 1). Is this a bug or a planned feature?
This is quite annoying if you meant to book a place for just 1 person but accidentally click add twice!