Don't understand the way HA Url links with nginx

So i have my reverse proxy working fine in docker. Connects clients to HA running in a separate container. Access is via port 443 and this is forwarded by the router. HA is setup with trusted proxy. All working.

But, accessing my HA remotely works with these;

But not this:

I guess that’s a http thing and nothing to to with HA ?
when I enter

Nothing to do with HA. If you specify a port in HTTP/HTTPS, the :port must be written directly after the domain, before any /

thank you kindly