I wonder the same thing. The first quilt I ever attempted on my own came out of a book. It told me to cut tons of little strips. I didn't check the math and it was wrong. One strip was cut 1/4" to short. When I called my grandma she couldn't believe that I cut all of those strips instead of strip quilting it. So that quilt is still in a bag not finished because I got so frustrated with it and the strips being to short. That was the first and last time I followed instructions out of one of those books.