ngc digits could not plot the bboxinges for DetectNet.

I am using the digits from here, https://ngc.nvidia.com/catalog/containers/nvidia:digits
with command:
nvidia-docker run -p 5500:5000 -v /home/vxgu/mnist:/mnt digits_caffe:19.09

I am running the detectnet for dog detector, like in
https://github.com/dusty-nv/jetson-inference/blob/master/docs/detectnet-training.md

I can see the dog part in last two layers ,but the bbox-list did not output anything

what is the problem?
https://github.com/vxgu86/configSet/blob/master/imgs/Screenshot%20from%202019-11-11%2012-51-28.png