Extras will be visible on the Calendar page if they have been set to have limited availability. Such extras are always booked for a certain date. This way you will be able to see, for example, how many breakfasts are needed on a given date.
When clicking on the number of extras booked for any date on the Calendar page, a popup will appear with more information and a printable PDF version. The PDF will list room number and guest name for all bookings that has this extra option for the selected date.