You don't need to alter code at all...
So first reinstall the script so changes are undone.
Just go to the script's preferences (Plus! icon > Countdown Live > Preferences) and change the string which makes up the countdown tag:
PS: if you have questions about a script, always search the forum for existing threads about that script and post in that existing thread. Don't create a new thread for it... in this case: "[Release] Countdown Live (Latest: 1.0.140)"