"13.1" meaning in English

{
  "etymology_text": "The distance of a half marathon, 13,1 miles.",
  "forms": [
    {
      "form": "13.1s",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "13.1 (plural 13.1s)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Athletics",
          "orig": "en:Athletics",
          "parents": [
            "Sports",
            "Human activity",
            "Human behaviour",
            "Human",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "examples": [
        {
          "text": "Holonym: 26.2"
        }
      ],
      "glosses": [
        "A half marathon"
      ],
      "id": "en-13.1-en-noun-9inP6WTf",
      "links": [
        [
          "half marathon",
          "half marathon"
        ]
      ],
      "raw_glosses": [
        "(slang, abbreviation) A half marathon"
      ],
      "tags": [
        "abbreviation",
        "slang"
      ]
    }
  ],
  "word": "13.1"
}

{
  "etymology_text": "The distance of a half marathon, 13,1 miles.",
  "forms": [
    {
      "form": "13.1s",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "13.1 (plural 13.1s)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English abbreviations",
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English nouns",
        "English palindromes",
        "English slang",
        "English terms spelled with .",
        "English terms spelled with numbers",
        "English words without vowels",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Athletics"
      ],
      "examples": [
        {
          "text": "Holonym: 26.2"
        }
      ],
      "glosses": [
        "A half marathon"
      ],
      "links": [
        [
          "half marathon",
          "half marathon"
        ]
      ],
      "raw_glosses": [
        "(slang, abbreviation) A half marathon"
      ],
      "tags": [
        "abbreviation",
        "slang"
      ]
    }
  ],
  "word": "13.1"
}