GMAT OG 13th中一道problem solving数学题求解

GMAT OG 13th中一道problem solving数学题求解
原题如下：Acertain characteristic in a large population has a distribution that is symmetric about the mean m. If 68 percent of the distribution lies within one standard deviation d of the mean, what percent of the distribution is less than m + d?解析为：Since 68% lies between m- d and m+ d, a total of (100 - 68)% = 32% lies to the left of m- d and to the right of m+ d. Because the distribution is symmetric about m, half of the 32% lies to the right of m +d. Therefore, 16% lies to the right of m+ d, and hence (100 - 16)% = 84% lies to the left of m + d.疑惑：如果图形关于m对称，在m+d的右边不是该50%-32%= 18% 从而答案为82%吗？