If you’re using the Aeon Labs Multifunction Siren device handler that’s mentioned in the post above yours, there isn’t a setting for “ALARM” so what did you edit?
If you’re using that device handler, you can go into the device settings and choose a different track for the commands siren, strobe, and both. When you select the device as an Alarm in SHM, it will execute the both() command.
I can’t remember if there’s a built in track that plays 3 beeps so if there is and that’s what you’re referring to, all you have to do is set the device’s “both” setting to that track number and set the “turn siren off after” setting to 300 or use the setting in SHM to turn it off.
If you’re trying to use the custom beep feature to beep for 5 minutes, you should select the device in the Audio Notifications section instead of the Alarms section.
Choose “Custom Message” from the Notification field and enter a custom command into the “Play this message” field.
Use the command shown in bold below to play 3 beeps every 7 seconds for 300 seconds (5 minutes) at volume 2:
7, 300, 3, 2, 3, 500, 50
The documentation that lists and explains all the custom commands is located: