This problem only appears in one document (I think).

I enabled "Readability Statistics" while working on document X. Now, for document X:

1. The Spelling and Grammar check detects no spelling and grammar errors (and there are indeed errors);
2. While the "Readability Statistics" are indeed displayed, all fields are 0 except for "words", "characters", and "paragraphs". These numbers are all too low and, get this, they are not constant - they sometimes remain the same upon re-run of the test, and they sometimes change. But they are always wrong in the sense of being too low.
3. Word Count appears to function properly.

Ctrl+A to select all text.
Then under the Reviewing Tab under Language check the proofing language setting.
If the box for "Do not check spelling or grammar" is not clear (empty) click on it until it is.
Run spell check again.
Mastering the Spelling Checker

Please let us know what you see.

I did exactly as you instructed, although that meant making no changes since "Do not check spelling or grammar" was already clear. When I ran the spelling and grammar check again, the problem persists although, strangely, this time spelling errors in my comments were detected. It may be relevant to know that even though I selected Ctrl-A before running the spelling and grammar check, I got a message like "Do you want to check the rest of the document?". I responded in the affirmative. The same problem appear in other documents (even though I reported otherwise before): even though the Ctrl-A does select the entire document, I get the behaviour reported in my first post: all readability metrics = 0 except for the first 3. And these are all wrong (in the sense of being way too low).

Solved my own problem. Thanks anyway.

Would you mind telling us what fixed the problem?

__________________
Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional

More than happy to explain. The first thing I do is select all text in the document using Ctrl-A. I then run the spelling and grammar check. After all spelling and grammar changes are processed, I am then, mysteriously, asked if I want to continue the check on the rest of the document.

What rest? I had selected the whole shebang.

Anyway, by trial and error I discovered that if I answer "no", then the readability statistics are correct. If I were to answer "yes", the readability statistics are incorrect. It makes no sense to me why I am being asked about the rest of the document given that I had selected all the text - there is no "rest of the document" as far as I can tell.

Thanks for your interest.

Thanks for the follow-up.

Note that pressing Ctrl+A, when the insertion point is in the main body of the document, will select the main body of the document, only. It excludes content inside text boxes or shapes and it excludes the content inside headers and footers.

__________________
Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional