De man pstree
:
pstree visually merges identical branches by putting them in square
brackets and prefixing them with the repetition count, e.g.
init-+-getty
|-getty
|-getty
'-getty
becomes
init---4*[getty]
Child threads of a process are found under the parent process and are
shown with the process name in curly braces, e.g.
icecast2---13*[{icecast2}]
-
[]
denota ramificações idênticas. -
{}
denota segmento filho.
Portanto, n[{process_name}]
significa que você tem n encadeamentos no processo pai process_name
.