gitlab-ce omnibus docker behind a local nginx reverse proxy (letsencrypt ssl termination at local nginx)

docker-compose.yml

version: '3'
services:
  gitlab:
    image: gitlab/gitlab-ce:latest
    hostname: gitlab.example.com
    environment:
      GITLAB_OMNIBUS_CONFIG: |
        external_url 'https://gitlab.example.com/'
        nginx['listen_port'] = 80
        nginx['listen_https'] = false
        letsencrypt['enable'] = false
        gitlab_rails['gitlab_shell_ssh_port'] = 31022

        registry_external_url 'https://registry.example.com/'
        registry_nginx['listen_https'] = false
        registry_nginx['proxy_set_headers'] = {
          "X-Forwarded-Proto" => "https",
          "X-Forwarded-Ssl" => "on"
        }
    ports:
      - '31080:80'
      - '31088:8080'
      - '31022:22'
    volumes:
      - './config:/etc/gitlab'
      - './data:/var/opt/gitlab'
      - './logs:/var/log/gitlab'

nginx.conf

server {
  listen 443 ssl;
  server_name gitlab.example.com;

  ssl on;
  ssl_certificate /letsencrypt/fullchain.pem;
  ssl_certificate_key /letsencrypt/live/privkey.pem;

  location / {
    proxy_read_timeout      300;
    proxy_connect_timeout   300;
    proxy_redirect          off;

    proxy_set_header        Host                $http_host;
    proxy_set_header        X-Real-IP           $remote_addr;
    proxy_set_header        X-Forwarded-For     $proxy_add_x_forwarded_for;
    proxy_set_header        X-Forwarded-Proto   https;
    proxy_set_header        X-Frame-Options     SAMEORIGIN;
    proxy_pass http://127.0.0.1:31080;
  }
}

server {
  listen 443 ssl;
  server_name registry.example.com;

  ssl on;
  ssl_certificate /letsencrypt/fullchain.pem;
  ssl_certificate_key /letsencrypt/privkey.pem;

  location / {
    proxy_read_timeout      300;
    proxy_connect_timeout   300;
    proxy_redirect          off;

    proxy_set_header        Host                $http_host;
    proxy_set_header        X-Real-IP           $remote_addr;
    proxy_set_header        X-Forwarded-For     $proxy_add_x_forwarded_for;
    proxy_set_header        X-Forwarded-Proto   https;
    proxy_set_header        X-Frame-Options     SAMEORIGIN;
    proxy_pass http://127.0.0.1:31080;
  }
}

The port format is "HOST:CONTAINER", should '22:31022' at line 23?

what's in port 8080 ?

Thanks