According to the Vysochanskij–Petunin inequality, for any unimodal and continuous distribution with mean $\mu$ and standard deviation $\sigma$, the probability of an observation falling outside $k$ standard deviations from the mean is bounded by $P(|X - \mu| \ge k\sigma) \le \frac{4}{9k^2}$ for $k \ge \sqrt{8/3}$. For a unimodal dataset of student test scores with mean $\mu = 75$ and standard deviation $\sigma = 6$, what is the maximum percentage of scores that can lie outside the interval $[63, 87]$?