If you select and click on Display Setting, a drawer opens in which you can set Row Display and Unallocated Bookings. Units can be grouped and displayed by the selected levels: Property and/Unit Type.
The Calendar includes both current and future Unallocated Bookings by default. If you select Also Include Past Unallocated Bookings, the past bookings will be displayed too.
Note that deselecting them will hide the corresponding rows on the Calendar.