In high-school, I played the snare drum in our marching band. When you’re on the field, if you are instep and in the correct place, but everyone else is out of step, and in the wrong place, guess who the crowd thinks screwed up? Measuring can be thought of the same way. If you do one piece correct, but everything else ends up off, then the one correct piece can become an eye sore. To fix that, cut your first piece, and use that as a reference for every other piece. The measurements on your plans are more like guidelines. I am in accounting at my full time job, and I like numbers to match up to what they are supposed to be, so I’ve had a hard time adapting to this myself, but it works.