dice score greater than 100

I have been trying to run the example code on SCGMChallenge dataset
I see that the dice score is computed using scipy 
Since the preds and gt_npy are not boolean arrays the outcome of dice dissimilarity is sometimes negative 
d  -0.1138425519461516
Then the dice score (1-d) is more than one as below
d1  1.1138425519461517

The resultant is that the dice score is more than 100 
