If both GitLab Runner and Executor are Docker, How the `volumes` mount?

If both GitLab Runner and Executor are Docker [1], [2] How the volumes in the config.toml mount? Will it mount to the path inside the GitLab Runner or the path on the host machine?

version: '3'

networks:
  default:
      name: some-network
      external: true

  gitlab-runner:
    image: gitlab/gitlab-runner:latest
    restart: always
    environment:
      - TZ=Asia/Bangkok
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
      - /path/to/config:/etc/gitlab-runner
[[runners]]
  executor = "docker"
  [runners.docker]
    image = "maven:3-eclipse-temurin-17"
    volumes = [
      "/cache",
      "/path/to/somwhere:/path/in/contianer" <---- Where the source path will be mount? 
                                             <---- inside the Runner or the Host Machine?
    ]

[1] Run GitLab Runner in a container | GitLab
[2] Docker executor | GitLab