It's about as likely that it is an African proverb as it is to be an original quote by Geneen -- meaning, it is unlikely to have been written down in the first. So, Geneen would be the first to have written it down -- that doesn't mean it was his quote.
Even Geneen's quote is not exact -- Geneen's work is never sourced with that quote -- except on "Wikiquotes" (take it likely if that is your source). In fact, the body of Geneen's work is cited in academic articles approximately about 500 times or so. Whereas, the attribution of the quote (minus an article "the" before the first mention of numbers) is given to Du Bois nearly 4k times and mostly indicated as "having known to have said".
Anyone can imagine that African proverbs are less likely to reach textual entities because of the auditory and oral mechanisms of knowledge production in such cultures and, thus, are often not attributed to a specific person.
Whereas Geneen takes the words as his, adding a little flavor to it in the form of an article. Du Bois is never cited as having the article.
Given the usage of demography and numbers in the earliest of Du Bois's work as well as his data visualization (which is well-documented), it is curious to resist attributions to Du Bois merely because he -- as stated by an earlier post -- was "not good at numbers". A closer reading of Du Bois's actual work would refute this claim altogether and strongly so.
Perhaps, Geneen should be cited as well with the page number, year, and the additional article. However, to dismiss the widespread attribution of the quote to Du Bois given that it most likely is a production of oral histories and mechanisms seems questionable and a narrow understanding of how knowledge is produced. Only 18 people even cite Geneen's book on management, which means it had nearly zilch influence on how people think about the effect of mastering numbers. The same cannot be said for Du Bois.