Marking thread as read

[Alshehhi Family]

I am new to gnus. I am trying to mark a thread as read. However, it is
still unclear to me how to do that. There is the command
gnus-summary-kill-thread:

        gnus-summary-kill-thread is an interactive native-compiled Lisp
        function in ‘gnus-sum.el’.

        (gnus-summary-kill-thread &optional UNMARK)

        Mark articles under current thread as read.
        If the prefix argument is positive, remove any kinds of marks.
        If the prefix argument is zero, mark thread as expired.
        If the prefix argument is negative, tick articles instead.

It seems that like it is the right command because it says "as
read". But when I run it, gnus mark the thread as kill. Am I missing
something?

Husain