Userlist count is a language string. You can override it using language overrides as described below.
www.joomlapolis.com/blog/kyle/18701-language-overrides-have-arrived
That specific string can be one of the two language strings.
Key: SITENAME_HAS_TOTAL_REGISTERED_MEMBERS
String:
Code:
[SITENAME] has %%TOTAL%% registered member|[SITENAME] has %%TOTAL%% registered members
Key: USERS_COUNT_MEMBERS
String:
Code:
%%USERS_COUNT%% member|%%USERS_COUNT%% members
Both can also be made userlist specific instead of sitewide using the below language keys.
USERLIST_{user list id}_TOTAL_REGISTERED_MEMBERS
USERLIST_{user list id}_COUNT_MEMBERS
So for example if my userlist has an id of 4 the above would be as follows.
USERLIST_4_TOTAL_REGISTERED_MEMBERS
USERLIST_4_COUNT_MEMBERS
You can override to an empty string as well to completely hide that if you like.