According to the documentation the fences are supposed to be drawn at Q1-1.5IQR and Q3+1.5IQR. The hover values in the following screenshot do not match this description:
Here, Q1 = 72, Q3 = 81, IQR = 9, Q1-1.5xIQR = 58.5 and Q3+1.5xIQR = 94.5. The lower and upper fences are drawn at 65 and 87 respectively. This is not correct and/or not consistent with the documentation.