Once upon a time, there was a fun, spring-y knitting project kit that used a fun, spring-y variegated yarn with delightful thick and thin sections.  The project was a cowl (with 2 size options) that utilized the thick-and-thin yarn with a coordinating variegated yarn of a uniform thickness. The two yarns alternated with each other in a slip stitch pattern called linen stitch — making a lovely mottled sort of fabric with random puffs — almost like blossoms!

The knitter considered knitting the larger size, but was dissuaded by her knitter-daughter (who had knit up the same kit in the smaller size with tremendous success and speed).  A compromise was attained whereby the knitter would make up the cowl at about 2/3 of the larger size and the arithmetic was achieved and the suitable (and, we must note, fairly arbitrary) number of stitches were cast on.

The knitter knit.  The knitter knit happily.  The knitter knit happily until the cowl was about 4 inches tall.  Then, the knitter noticed something odd about the fabric of the cowl.  Instead of being a lovely mottled sort of fabric with random puffs like blossoms, the fabric was a mostly dull and flat with herds of puffs lining up in 3 distinct columns!  It did not look fun and spring-y.  It looked like an inexpensive upholstery of not the best taste.

The thick-and-thin yarn was stacking!  Stacking is a phenomenon whereby a yarn dyed with different colors at regular intervals (as in most hand-dying techniques) is knit in such a way that the colors form columns.  To quote Laura Militzer Bryant"s excellent book Artful Color Mindful Knits :

"Stacking occurs when gauge, repeat, and stitch count all conspire so the full repeat is used within one row and then begins again, causing colors to stack on top of one another.  The number of stitches needed to cause stacking is what I refer to as the Magic Number.  Precise stacking requires constant small adjustments to stay as close to vertical as possible, so attention must be paid to tension."

The Magic Number!  Somehow the knittter had miraculously happened upon the Magic Number for this yarn (which had clearly been formed to thicken and thin-en at regular intervals) when worked in linen stitch on US size 11 needles:  175 stitches!  Now, if she had ascertained this number intentionally following the methods she had learned in Laura Militzer Bryant's excellent workshop (which she and her knitter-daughter had attended a few years ago), then she would have been a genius!

As it was, however, she was simply unlucky.  For the Magic Number was forming three armies of puffs that would march relentlessly up her torso and neck if she continued to knit the cowl the way it was.  There was nothing to do but text her knitter-daughter with many tearful and enraged emojis.  The knitter-daughter arrived, made soothing noises, and ripped back the cowl.  A new — and decidedly un-magical — number was decided upon:  161.

And the knitter heaved a substantial sigh, poured a substantial glass of Pinot Gris, and cast on 161 stitches.