Tool 20 is brilliant. Choose the number of elements with a purpose in mind. Here's a sentence with one defining characteristic.
"That girl is smart."
What's the effect? The reader must focus on one quality.
Let's look at sentences with three and four elements. Three elements provides a complete picture, a sense of the whole. Mr. Clark uses this example:
"That girl is smart, sweet, and determined."
From William Shakespeare, the power of three: "Friends, Romans, countrymen, lend me your ears."
Now, consider the effect of four or more elements. Three elements provides a greater sense of completeness. When you use four elements you break out of the circle of completeness. Four or more elements can provide a flowing, literary effect.
"That girl is smart, sweet, determined, and neurotic."
When to use three or four elements.
Use three for completeness, wholeness. Four or more to list, compile, and expand.