How to pass alarm custom property into calculated alarm roster

I’m trying to create an alarm pipeline for a UDT using a calculated roster. However, I’m having trouble getting the machine ID parameter from the UDT passed into the calculated roster when the alarm event occurs.

I created a custom property within the triggering alarm which references the machine_id integer tag that I’d like to pass into the calculated roster script. However, I can’t find how to reference this custom property within the calculated roster script.