Timestamp calculation

Configuration
,
1

Hi all,

I am using a laudrify adapter to monitor my wahser/dryer.
I have a problem with the message of my automation.
When the devices are done, i get a message via telegram that is is ready.
My “problem” is that i always get as running time 1:00:00

alias: Waschmaschine Simple
description: ""
trigger:
  - platform: state
    entity_id:
      - binary_sensor.meine_waschmaschine
    to: "off"
    from: "on"
  - platform: state
    entity_id:
      - binary_sensor.meine_waschmaschine
    from: "on"
    to: unavailable
condition: []
action:
  - service: notify.all_telegram
    data:
      message: >-
        Meine Waschmaschine ist fertig nach {{ (now().timestamp() -   
        as_timestamp(states.binary_sensor.meine_waschmaschine.last_changed))  |
        timestamp_custom('%H:%M:%S')}} Stunden
    enabled: true
mode: single

i believe my problem is that this is triggered everytime when it is done (last changed), but it’d need the second_to_last_changed state resp. the last time it changed to running and not done.

What would be the right formula for the time calculation in my message?
Thanks a lot
wasty