For the loss you only care about the probability of the correct label. In this case, you have a minibatch of size 4 and there are 10 possible categories to choose from (hence the (4L, 10L)).
If you recall the cross-entropy loss, it is: log(probability(correct_label)), summed over the minibatch. So the labels are just 4 integers (one per sample in the minibatch) between 0 and 9 (since you have 10 labels).