Bookings: offer only limited dates to be visible and bookable by customers

I'm new to Bookings and it looks to have a lot of good features for my team's needs but I'm stumbling at calendar setup.  We run various training courses, each several days long and offered once every couple of months.  I can't find the right Availability Options to make course dates visible and bookable.  With Not Bookable, no dates appear, with Bookable When Staff are Free, all dates are available.  I've tried using Not Bookable with different availability for a date range and that sometimes appears but then the booking page message says that the customer can book any start time they wish during the session time. 

What am I missing?  Or is this tool not open to this type of use...?