Meaning.

He's noting his surroundings, one by one, in extraordinary detail. He notes the four kids, details all their characteristics. That done, he moves on to a woman with a dog, and evaluates her in detail. And so on.

Anonymousil. He notes the four kids, details all their characteristics. That done

Done = check, finished.

To me, it seems like an obsessive-compulsive person going through his mental checklist, and checking off his obligations to observe his surroundings in minute detail.

Thanks for the replies.There remains in my mind two other questions about the same text.One is the meaning of pack of wolves in this context Does it refer to the four kids? Second,the age, rank,serial number,pecking order and hierarchy is related to the characteristics of the kids? If so, does the phrase " established before the age of six" means that their age was before six? I appreciate rec

Then he noted the four kids playing in the park cross the street.
Age (what was the age of each kid?)
rank, (which kid was the leader, which kid was next in line to be the leader...)
serial number (how each kid could be identified) ,

pecking order, (which kid could boss the others the best; which kid would have to do the dirty work)
and hierarc