EfficientNMS_TRT occasionally chooses the one with the second highest confidence category

Description

I use yolov9 model with EfficientNMS_TRT to inference, and I’ve found that certain boxes won’t select the category with the highest confidence, but rather the category with the second highest confidence.

Is this likely to happen? what is the internal processing logic of EfficientNMS_TRT?

for example:

These are the first five categories of confidence for the three boxes, but the output category for EfficientNMS_TRT is 5, not 0.

anchor1: 0.273078 0.000085 0.000005 0.000101 0.000071 0.266680
anchor2: 0.448257 0.000038 0.000004 0.000012 0.000069 0.255931
anchor3: 0.378077 0.000077 0.000005 0.000034 0.000093 0.254360

Environment

TensorRT Version: 8.5.3
GPU Type: GeForce GTX 1080
Nvidia Driver Version: 535.146.02
CUDA Version: 11.8
CUDNN Version: 8.6
Operating System + Version: ubuntu18.04