Each time someone types @Trigger this script would respond. If several people have this same script, then someone typing @Trigger gets a reply from several different scripts.

If you don't assign it a specific name, the timer is given the first available number starting with 1. So since this command is in a location which executes each time someone types @Trigger, it causes a new timer to launch.

Timers are not located in a script, so they don't get canceled when the script unload. I suggested in https://forums.mirc.com/ubbthreads.php/topics/264317/Cancel_script's_timers_/unload#Post264317 that it be an option, because timers often contain names of aliases only existing in the script being unloaded. If you had typed "/timer" you would have seen a list of all the timers running, and you could cancel them by name like "/timer1 off" or can replace the 1 with another nane or even a wildcard.

What you want is at least 1 of the following.

* only create the timer if it does not already exist
* have someone types something that doesn't make several people respond to them.

Code:
on *:text:@Trigger &:#ChannelA:{
  if ($2 != $me) return
  /notice $nick Latest List at: http://example.com
  if (!$timer(mylist)) /timerMyList 0 300 /msg #ChannelA for my list Type: @Trigger $me
}


The & is a wildcard symbol matching 1 word, so this responds only to someone typing a word following @Trigger, and the first command of the event checks to see if that word is your current nick.

This gives your timer a name, and it checks that a timer by that name doesn't exist before starting it. You want to assign it your own name, because if you don't assign it a text name, it gets assigned a number instead, and that can be a little harder for scripts to deal with. $timer(xyz) refers to the namer named xyz, but $timer(7) refers to the 7th timer in the list instead of timer7.

This timer doesn't check to make sure you're in the channel or that you're even at the correct network. You could add lines to check that, such as:

if ($network != value) return
if ($me !isin #ChannelA) return

By default, timers are cancelled when you disconnect from the network where they're running, unless you use the -o switch as mentioned in /help.

You can use F1 to access mirc's /help system, or type /help /timer or /help $timer to get more information on those specific topics.

As mentioned in https://www.mirc.com/help.html the Wiki at is still being created, but often has more detailed help and examples than found in /help
http://en.wikichip.org/wiki/mirc

You can also search in the forum for posts related to other people asking about the same topics. If you search for more than 1 keyword, it returns posts that mention at least 1 of the keywords. If you want only posts mentioning both, you need to search for +keyword1 +keyword2. You also need to change the time from the default 1 year, to find older posts.