Each piece of bar indicates the number of people interested in a particular event and when they may be available to attend.
The bigger the piece of bar the more popular the event x time combination. Hopefully it makes sense to focus on the more popular first (i.e. Adult events Sunday-Thursday evenings) and work down the popularity as we want to add more events.
However, of course anyone who wants to organise any event is good. Hopefully this chart with give you and idea of which events and times may get a better turn out.