Number of samples and Frequency per samples Vs. Number of Features and Frequencies per Features

I am wondering why there are not written my samples names under the each histograms while I dedicated a description column for my samples.

I found a Qiime2 user's graphs mentioned his samples names.

How is Qiime2 able to name samples? What should I do to name my samples automatically by Qiime2?

Thnx