Confused with the naming scheme of sensors in HA

[alexanderfitu]

Sorry If I am being dense. I have read through the docs a few times and am a bit stuck on the logic of a few things.

I have one monitor device (at the moment) and plan to use device_tracker platform as mentioned in the docs.

I would like to understand the choices behind some things though.

I have the monitor running and its sending mqtt messages to the broker which is being succesfully written to the state topic, as below:

• platform: mqtt
  state_topic: 'monitor/first floor/phonename'
  value_template: '{{ value_json.confidence }}'
  unit_of_measurement: '%'
  name: 'First Floor'

However, I am getting one sensor named "First floor". I know this is because I have named it first floor. Surely this sensor should be called "phonename" as its monitoring the topic named after the devices its monitoring?

Additionally, I would need a "state" for each device?

As I plan to expand the system, I want to ensure I can wrap my head around it.