I guess these numbers are  the average of all images from imagenet
it’s doing something of reverse-transform or unnormalize  which transform the data to range(-1,1).

  
      github.com
  
  
    pytorch/examples/blob/master/imagenet/main.py#L116-L117 33

normalize = transforms.Normalize(mean=[0.485, 0.456, 0.406],
                                 std=[0.229, 0.224, 0.225])