Why is the queue announced full while there is still a free space left in circular queue?

There could be a few reasons for this. It's possible that the announcement was made prematurely or that there was a miscommunication between the system and the announcement. It's also possible that the free space left in the circular queue is too small to accommodate any more items or that it's reserved for a specific purpose. Nevertheless, without knowing the specific details of the situation, it's difficult to give a more precise answer.