Why do some TV Shows have genres that are not in the tv genres list

https://api.themoviedb.org/3/genre/tv/list?api_key=<KEY>

Using methods like discover

https://api.themoviedb.org/3/discover/tv?api_key=<KEY>&sort_by=popularity.desc&page=2&include_null_first_air_dates=false

returns results with genre ids (28) that can not be mapped to the list of tv genres

 {
      "original_name": "Arrow",
      "id": 1412,
      "name": "Arrow",
      "popularity": 44.069,
      "vote_count": 1923,
      "vote_average": 6,
      "first_air_date": "2012-10-10",
      "poster_path": "/mo0FP1GxOFZT4UDde7RFDz5APXF.jpg",
      "genre_ids": [
        28,
        80,
        18,
        9648
      ],
      "original_language": "en",
      "backdrop_path": "/dKxkwAJfGuznW8Hu0mhaDJtna0n.jpg",
      "overview": "Spoiled billionaire playboy Oliver Queen is missing and presumed dead when his yacht is lost at sea. He returns five years later a changed man, determined to clean up the city as a hooded vigilante armed with a bow.",
      "origin_country": [
        "US"
      ]
    }