Readability, and Which Sentence Is the Problem PLAIN
Readability scores cannot tell whether a sentence means anything. What they are genuinely good at is finding the forty-eight word monster the writer cannot see.
What you wrote
The numbers
These count syllables and clauses. They cannot tell whether a sentence means anything, a good technical paragraph scores badly because the words it needs are long, and anybody writing to hit one of them is making their prose worse. They are here because the disagreement between them is informative: a fog index much worse than the rest means long words in short sentences, which is a different problem from long sentences.
What to actually change
The report
Questions people ask about PLAIN