I have a data set with about 500 features. Following the WGCNA tutorial, I got 19 modules. One of them is labeled as grey60, and I am a little confused whether this is unassigned or not. It is a small branch in the middle of below dendrogram (between two even thinner blue bars).

I read the documentation of labels2colors(). It seems that I shouldn't get any grey color if all features are assigned. I also checked the original module label, and there is no 0 module. Does it mean I can use this "grey60" as a regular module in downstream analysis?