an additional allowance added to the stick length of wider widths and subtracted from the length of narrower widths to help preserve the designed proportions of the forepart
But there is a second extension on some of the widths, for the purpose of preserving the general shape of the toe. … widening the shoe out to this extent without allowing anything for length would entirely change the contour and appearance of the forepart. This is allowed for in the lasts by adding slightly to the length up[ from the sample width, which is the standard, and decreasing slightly on the narrower widths.
…
…amounting usually to 1/8 to 1/4 of a size to each width.
— The Shoe and Leather Lexicon, Fourth Edition, 1918