If you followed the exchange of comments between myself and WAH, you know that he has defended Cheng by assuming that Cheng meant 40 kilometers, not 40 knots when describing the wind on April 12, 2003. WAH pointed out that the abbreviation for knots is kn, and the abbreviation for kilometers is km, and so a typo explains the mistake.
Is it possible that a simple typographical error could have caused the mistake? That's a question that most definitely must be answered, so I did some research.
Court Reporters use a stenotype machine, which does not have a regular typewriter/computer keyboard. I found a picture of the machine and a layout of its keys. I was quite amazed to find that the keys do not include the "m" and the "n".
The article explained that different theories are used to form the words, and the Court Reporters can also create their own shorthand for commonly used words.
However, with the "m" and the "n" being absent from the keyboard, the abbreviations "kn" and "km" could not be used in those forms. To form the abbreviation kn, the court reporter has to key K for the inital K and PB for the final n. To form the abbreviation km, the court reporter has to key K for the initial K and PL for the final m.
I've included a visual from a website, which incidentally is the same article that appears under this subject on Wikipedia, Answers.com, and a couple other websites. The article gives much more information.
If you wonder why some letters appear twice on the keyboard, it's because the keys to the left of the * are used to generate initial consonants, and the keys to the right are used for final consonants.
WAH, if you have information that shows a stenotype machine that does have the m and n keys, please post it.