Hello all,

FastAI version: `fastai==1.0.60`

I noticed that when I plot the confusion matrix (on my validation set) and sum the numbers that it does not correspond to the number of items in my validation set.

Example:

The confusion matrix (array):

```
array([[50, 13],
[ 0, 65]])
```

Adding the numbers above = 50 + 13 + 65 = 128

The number of items in the validation set:

```
learn.data.valid_ds
LabelList (140 items)
x: ImageList ...
```

I would expect these two values to be the same or am I missing something?

Thanks!