The calendar shows only the Public, Preston related, events. Many events at Preston are Private and you will find the Centre is busier than it seems from the calendar.
You can change the view using the button on the top right hand side of the calendar. If you do not like the month view then you might switch to another view. Perhaps the Agenda view which give a list of events. Look around and see which view suits you best.
If you are in the habit of using an electronic calendar, on your phone or tablet for example, then you may want to subscribe to this calendar so that Preston events are visible in your own calendar. The subscribe button is at the bottom right.