Help needed with "cert_expiry"

What is the proper way to set “cert_expiry” host|???

host: mydns.duckdns.org - with this, the badge displays, “-” ‘’(1 dash)
or
host: duckdns.org - with this’ the badge displays “236”, which is too high

I use this:

# Certificate LetsEncrypt
  - platform: cert_expiry
    host: !secret my_letsencrypt
    port: 8123

Note this only updates every 12 hours (I think) so it can show a -

hahaha Just noticed it’s in the secrets file! Not helpful!
host: my-domain.duckdns.org

Thank You, for the clearity… I will add the “port” setting and the rest, like you show, tnen wait 12+ hours…

In my search, I have seen several different examples, including one with,
host: home-assistant.io

I