No worries. It can be a bit confusing.
Currently, your Nextcloud is listening to HTTP (i.e. no TLS) on port 443.
Ideally, it should listen to HTTPS (i.e. with TLS) on port 443. I am not sure why it isn’t.
They are telling you that, by default, the Nextcloud container does in fact listen on HTTPS. Yours for some reason is not exhibiting the default behaviour.
Feel free to link them to this post by way of explanation (click the timestamp up the top right of this post for a shareable link).