From the help file:
'If you are not connected to a server and you start a timer, it defaults to being an offline timer which means it will continue to run whether you are connected to a server or not.
If you are connected to a server and you start a timer, it defaults to being an online timer, which means that if you disconnect from the server, it will be turned off. You can specify the -o switch to force it to be an offline timer.'