Even though dishcloth patterns state 100% cotton yarn, many times other yarn with 50% cotton or more is better. A cotton blend will hold its shape better after use or washing. I usually purchase yarn in a cone and it is a blended cotton. Also, yarns that are category 4 sometimes are thinner or thicker than others in the same category. I don’t know why, but they are. Some are softer than others. Try to purchase a medium thick yarn.
If in doubt, look it up on the internet and do research on yarns.