Is this a BUG in torchmetrics when calculating FID?

I use the same input into the torchmetrics.image.fid.FrechetInceptionDistance, the value should be zero, while I got some output like tensor(-8.8290e-06, dtype=torch.float64). Is this a BUG?
Here is my code:

from torchmetrics.image.fid import FrechetInceptionDistance

fid = FrechetInceptionDistance().set_dtype(torch.float64)
imgs_dist1 = torch.randint(0, 255, (100, 3, 256, 256), dtype=torch.uint8)
fid.update(imgs_dist1, real=True)
fid.update(imgs_dist1, real=False)

Here is my output:
tensor(-8.8290e-06, dtype=torch.float64)