I agree that you would make a narrow hem first, then turn for the finished hem. However, this can be more tricky than it seems because the width of the sleeve is probably not even. In other words, when you turn so the hem is the desired size, you may find that the edge is smaller than the sleeve. I did this a couple of times for dh, then told him no more. It was too difficult to get a nice-looking hem. Now he has to either buy new shirts or wear cut-off unhemmed sleeves.