Hi @Matilda_H-D,
Yes! N = the number of distances measured. So you have 24 supra, 9 sub, and 1 supra_sub.
Sub total N = sum of all integers ≤ 9 = 36
Supra total N = 24 * 9 = 216
Supra_sub total N = 1 * 9 = 9
One boxplot is output for each group G; the distances between each sample in group G and each other sample are shown. So in the plot you shared above, each box and whisker is showing the distribution of distances between each sample in group “sub” and each other sample.
I hope that clarifies! 