To add to that, you also superfat higher if your soap might have a tendency to be very cleansing, like if you use a higher amount of coconut oil and/or very less conditioning oils.
Coconut oil once it's saponified is very good at stripping skin off dirt and oils, which unfortunately you still need to not get that tight feeling.
Some have made recipes with low coconut and therefore low superfat, because there is not much need to compensate for the stripped off oils. Some soap which require a high percentage of coconut, like salt soaps have a higher superfat.
It's all about learning what works for your skin. Once the calculators have computed your superfat for you, just remember that the numbers don't account for the superfat. So let's say you have a very low cleansing number to begin with, a high superfat might lead to a greasy feeling soap.
Here's a
great read on superfat, by this forum's very own DeeAnna, and while you're there I suggest going through the whole site. There's a ton of info that will help you get started on trying your first soap