aggregate agent grpsum help

[zozo]

Hello,

I have create an item for the asterisk calls called asterisk.calls which I am using to create graphs for the number of calls on each server.
I would like to use grpsum to get the information from all asterisk servers and show the number of total calls in a graph. I would like to know if the format I am using is correct and where should I create this item.

the key I am using looks like this:

grpsum["Production","asterisk.calls","last","0"]

thank you in advance for your suggestions

[zozo]

I have created an items into the zabbix_linux template where the asterisk.calls is but after some times the servers on which is assigned they are getting Not supported. Is there any help or suggestions?