Mismatch between result message and result image

[yes89929]

I made custom dataset that has 3 classes.

And, I trained hrnet model with pretrained weights.
python train.py --gpus 0,1,2 --cfg config/ade20k-hrnetv2.yaml

Then, I validated a one image used training.

Output message is Mean IoU: 1.0000, Accuracy: 100.00%

But, when looking result image, it's not.

I printed number of pixcel in intersection and union.
And, number of gray pixcel is 12614.
However, it is must be > 1,000,000, considering result image.

### intersection: [12614 4295 3970] union [12614 4295 3970]

I have no idea what is problem.