I think that when the package states, 'For tap sizes #0-1/2"', it is referring to the size of the holes that the taps would be used for - and not to the square shank sizes. So, as small as a tap for a #0 hole, and as large as a tap for a 1/2" hole.
As one point of reference, you might look at some of the tap wrenches at McMaster-Carr. They show not only the range of tap sizes, but also the range of square shank sizes.