You count the dots. The number of dots tell you how many of each length of string she used.
You first find the column with the most dots, and then you find the column with the least. Then you just subtract them, the number of inches it displays on the bottom, 12 1/2 - 12 1/4, which is 1/4. I did this in my head and you can use a calculator if you want.
Thanks for the points, and have a blessed day. Hope this helps.
