Why was the number $73.2$ used in "Sharper bounds for the Chebyshev functions $\theta(x)$ and $\psi(x)$. II" in theorem 10, inequality 6.2?

Question

In Schoenfeld's paper "Sharper bounds for the Chebyshev functions $\theta(x)$ and $\psi(x)$. II," theorem 10, inequality (6.2) states "If the Riemann hypothesis holds, then $|\psi(x) - x| < \frac{1}{8\pi}\sqrt{x}\ln^2{x}$ if $x > 73.2.$ However, it is true for $59 < x \le 73.2$. Why was the number $73.2$ used?