When the net weight of the thread in or on any unit is less than two (2) ounces avoirdupois, the unit shall be marked to show the length of the thread in yards as unwound from the unit. Ready-wound bobbins that are not sold separately shall not be required to be individually marked, but the package containing the bobbins shall be marked to show the number of bobbins contained in the package and the net weight or measure of the thread on each bobbin. Any retail unit of thread, sold only for household use, consisting of a package containing two (2) or more similar individual units, that are not sold separately, shall be marked to show the number of individual units in the package and the net weight or measure of the thread in each individual unit, but this provision shall not apply where the individual units are separately marked.