Sensor that render list of items. How to process data?

Configuration
1

I created a template sensor that generates a list of rooms to be vacuumed.

              {% if is_state_attr('sensor.tracker','home_zone', true) %}
                {% set rooms = [] %}
                {% if is_state('sensor.tracker','not home') or
                        states('sensor.before_alarm_time') | int(default=0) > 3600 and 
                        states('sensor.before_alarm_time') | int(default=0) < 7200 and 
                        is_state('binary_sensor.door_sensor_br_contact','off') %}
                  {% if (as_timestamp(state_attr('timer.vacuum_lr','finishes_at'), as_timestamp(now())) - as_timestamp(now())) | int < 43200 and
                        is_state('sensor.tracker','not home') or is_state('timer.vacuum_lr','idle') %}
                    {% set rooms = rooms + [16] %}
                  {% endif %}
                {% endif %}
                
                {% if is_state('sensor.tracker','not home') or
                      is_state('input_select.human_location','Living room') and 
                              is_state('binary_sensor.door_sensor_br_contact','on') %}
                  {% if (as_timestamp(state_attr('timer.vacuum_br','finishes_at'), as_timestamp(now())) - as_timestamp(now())) | int < 43200 and
                        is_state('sensor.tracker','not home') or is_state('timer.vacuum_br','idle') %}
                      {% set rooms = rooms + [18] %}
                  {% endif %}
                {% endif %}
                
                {% if is_state('sensor.tracker','not home') or
                      is_state('input_select.human_location','Living room') %}
                  {% if (as_timestamp(state_attr('timer.vacuum_hall','finishes_at'), as_timestamp(now())) - as_timestamp(now())) | int < 43200 and
                        is_state('sensor.tracker','not home') or is_state('timer.vacuum_hall','idle') %}
                      {% set rooms = rooms + [17] %}
                  {% endif %}
                {% endif %}
                {{rooms}}
              {% endif %}

However, I am not able to decode this data afterwards
I try:

{{ states('sensor.vacuum_cleaning_shedule_list') | count }}

that render 4 , when for example sourse sensor render [16].
Looks like it’s counting character counts instead of items

Also it is not clear to me how to check if there is a specific item in the list

Thanks

2

You can’t do like that.
You need to use a namespace list