The empirical rule tells you 68% of the population is within 1 standard deviation of the mean. Your limits are 1 standard deviation from the mean, so your percentage is ...
... 68%
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98.20 - 0.62 = 97.58 . . . 1 standard deviation below the mean
98.20 + 0.62 = 98.82 . . . 1 standard deviation above the mean