@Shyam0 This is not a bug and the system is designed to work this way. The reason for this is that you might want, in high season, to block the listings for each room hence targeting the whole cottage listing.
If you haven't already done so I would urge you to switch on pro tools in your account. By doing this you get the multi calendar which makes it very easy to see what is booked, what is blocked and what is available.