Issue the command:

REVIEW listname SHORT NOHEADER


You should get a response something like this:

Date:         Wed, 02 Sep 2020 14:30:32 -0400

From:         "LISTSERV.EXAMPLE.COM LISTSERV Server (17.0)"

             <LISTSERV@LISTSERV.EXAMPLE.COM>

Subject:      File: "MYLIST-L LIST"

To:           Joe ListOwner <JOE@EXAMPLE.COM>


*

* Total number of "concealed" subscribers:         227

* Total number of users subscribed to the list:   4623  (non-"concealed" only)

* Total number of local host users on the list:      0  (non-"concealed" only)

*


The first number represents the number of subscribers who have set the "CONCEAL" personal option. You add the first number to the second number to get the total number of subscribers. In this case the list has 227 + 4623 = 4850 subscribers.

The third number represents only the number of subscribers who are subscribed from accounts on the LISTSERV server. In the "old" BITNET days when LISTSERV ran only on VM mainframes, this number could be significant. Today, when most LISTSERV servers run on dedicated workstation-type machines that do not have mail accounts on them, this number is usually zero.  If it happens to be non-zero, it can (and should) be ignored in the total count, because it represents a subset of the total number of subscribers indicated by the other two numbers.