"could not care less" meaning in English

{
  "forms": [
    {
      "form": "could not have cared less",
      "tags": [
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "verb",
        "3": "simple past",
        "4": "could not have cared less"
      },
      "expansion": "could not care less (simple past could not have cared less)",
      "name": "head"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "senses": [
    {
      "alt_of": [
        {
          "word": "couldn't care less"
        }
      ],
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English entries with language name categories using raw markup",
          "parents": [
            "Entries with language name categories using raw markup",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English negative polarity items",
          "parents": [
            "Negative polarity items",
            "Terms by semantic function"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English terms with non-redundant non-automated sortkeys",
          "parents": [
            "Terms with non-redundant non-automated sortkeys",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "Alternative form of couldn't care less"
      ],
      "id": "en-could_not_care_less-en-verb-Uwb5V1Ub",
      "links": [
        [
          "couldn't care less",
          "couldn't care less#English"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative"
      ]
    }
  ],
  "word": "could not care less"
}

{
  "forms": [
    {
      "form": "could not have cared less",
      "tags": [
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "verb",
        "3": "simple past",
        "4": "could not have cared less"
      },
      "expansion": "could not care less (simple past could not have cared less)",
      "name": "head"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "senses": [
    {
      "alt_of": [
        {
          "word": "couldn't care less"
        }
      ],
      "categories": [
        "English entries with incorrect language header",
        "English entries with language name categories using raw markup",
        "English lemmas",
        "English multiword terms",
        "English negative polarity items",
        "English terms with non-redundant non-automated sortkeys",
        "English verbs"
      ],
      "glosses": [
        "Alternative form of couldn't care less"
      ],
      "links": [
        [
          "couldn't care less",
          "couldn't care less#English"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative"
      ]
    }
  ],
  "word": "could not care less"
}