Keras model evaluation accuracy vs. observation
Actually, I think accuracy is not a good metric for this case as y_actual and y_expected have most values 0 and the length of y_actual is quite big too. 

So the accuracy calculation using an equation like K.mean(K.equal(K.argmax(y_true, axis=-1), K.argmax(y_pred, axis=-1))) (Reference) is not a good metric on model performance