Online Booking - Shorter Options "Offer Bookings...."

We would love to use our online booking to manage acute clients / emergencies. I currently manually have to release dates on a week by week basis as the shortest option is to offer appointments for up to 4 weeks, If this could be adjusted to 1 or 2 weeks instead it will prevent patients using it to book advance appointments and keep the slots free for the emergencies they should be left available for.