Then you don't understand that the mathematical probability remains the same whether you flip ten coins in one group, 15 coins in another, and 16 coins in still another group for a total of 3 intermediate steps, or one coin 41 times.
The final probability for randomly hitting a pre-determined outcome of 41 units is precisely the same either way.
That's what the math addresses: the final probability of data in a chaotic, unintelligent environment correctly sequencing itself. Except in this case, we're dealing with much lower probabilities of getting each correct character out of far more possibilities than a mere two sided coin toss...
Why does the author assume there there can be only a single monkey generating each fragment, and that that fragment cannot persist beyond a single trial?