Fortunately, they had already printed 5000 copies of the original 7500 copy run. So Kilcullen ordered the print run stopped at 5000 copies.
To his credit, Kilcullen did not halt the book after that initial sell out, and he did have the wisdom to keep printing the book. It took several months before the print runs were increased to 50,000 copies. Even then I recall Kilcullen expressing reluctance. At one point he told me how he was concerned about having 50,000 copies of DOS for Dummies in his garage forever.
Of course, that never happened.