Please take note that in January 2013 the backing fabric for the miniature kits was discontinued and an article posted stating that the price of the kit had been adjusted accordingly: you can find the article here.
The kit instructions originally instructed for you to use a backing fabric but I later decided this was not necessary and amended the kit instructions to reflect this. Unfortunately it seems that the printers have printed the original instructions for some of the previous kits.
Please accept my apologies this error will be corrected in the future, in the meantime if you have received a miniature kit that calls for backing fabric, ignore it! It is not necessary the main fabric is sturdy enough to use alone.