Pass variables start_conversation script

I’m attempting to get my VPE to let me know that my garage door has been open for X minutes and ask me if I want to close it. Thus far, I have been able to accomplish the notification, but cannot figure out how to pass specific variables into the start_conversation action.

I am using the custom integration NotiScript, which basically allows you to wrap a script so that it appears as a notifier to HA. This means that using the alert integration, I can do the following:

alert:
  inner_garage_door:
    name: Inner garage door open
    message: "Door has been open for {{ relative_time(states.cover.garage_door_inner.last_changed) }}"
    entity_id: cover.garage_door_inner
    state: 'open'
    repeat: 
      - 5
      - 10
      - 15
      - 30
      - 60
    can_acknowledge: true
    notifiers:
      - inner_garage_door_open
      - kitchen_voice_assistant_prompt

notify:
  - name: kitchen_voice_assistant_prompt
    platform: notiscript
    data:    # not sure if these last lines are correct
      door: "inner"
      elapsed_time: "{{ relative_time(states.cover.garage_door_outer.last_changed) }}"

Then, with a script, I do get a prompt on my VPE telling me the door is open and it will act on my response, however it does not seem to see the {{ variables }}.

script:
  kitchen_voice_assistant_prompt:
    sequence:
      - action: assist_satellite.start_conversation
        metadata: {}
        data_template:
          start_message: The {{ door }} garage door has been left open for {{ elapsed_time }} minutes. Would you like me to close it?
          preannounce: true
          extra_system_prompt: >-
            The user has left a garage door open and is being asked if they would
            like to close it.
        target:
          entity_id: assist_satellite.kitchen_vpe_assist_satellite

I have no doubt that I’m butchering this, but would appreciate any guidance on it.