'Free shipping' is somewhat of a misnomer. What it actually does
is to to exclude the weight or value of the item from total used to
calculate shipping, so the shipping price for the order will be the
same as it would be if the item was not in the order. To make sure
that an order with just a single item that is 'Free shipping' actually
gets free shipping, you should ensure that your shipping setup
includes a 'zero' band, resulting in a shipping cost of zero for order
weight/value up to 0.01 (or 0.001 for example).