Miscounting fs when "of" is present is actually a fairly well known psychological effect (see e.g. https://sharpbrains.com/blog/2006/09/10/brain-exercise-brain-

Miscounting fs when "of" is present is actually a fairly well known psychological effect (see e.g. https://sharpbrains.com/blog/2006/09/10/brain-exercise-brain-teaser/ https://sharpbrains.com/blog/2006/09/10/brain-exercise-brain...). It's because the sound of the letter is different, and that makes me think deaf people will be more likely to count correctly. I still prefer "The five boxing wizards jump quickly".