Nagios reports wrong


I use this service to check currently logged in users in one of my linux host but this always shows me 3 users currently logged in. In fact there are 75 users logged in. Am I doing right ? what are the check_command for checking remote hosts users, disk and services ?

define service{
use local-service ; Name of service template to use
host_name abc
service_description Current Users
check_command check_local_users!20!50