Suppose the gpa scores of the students in a class are normally distributed with a mean of 3.4 and a standard deviation of 0.2
We need to find how far 3.2 from 3.4
3.4 - 3.2 = 0.2 that is 1 standard deviation from mean (left)
Also we find how far 3.6 from 3.4
3.6 - 3.4 = 0.2 that is 1 standard deviation from mean (right)
As per empirical rule , 68% of values fall within 1 standard deviation from mean
so 68% of students in this class with a GPA Between 3.2 and 3.6