In the detection of unknown items, the detection results are shown in the figure below.Is the bucket not detected because the data set is different?

[bodhi-tree01]

In the detection of unknown items, the detection results are shown in the figure below. Is the bucket not detected because the dataset is different? If I use my data set for training, can I detect unknown objects?Roughly how many images are needed for the dataset? Looking forward to your reply. Thank you very much！