Elasticsearch Explain API中N值远大于实际文档数的问题

我尝试使用explain:true子句分析搜索结果的评分机制，发现idf计算结果如下：

{
  "value": 6.660968,
  "description": "idf, computed as log(1 + (N - n + 0.5) / (n + 0.5)) from:",
  "details": [
    {
      "value": 37,
      "description": "n, number of documents containing term",
      "details": []
    },
    {
      "value": 29298,
      "description": "N, total number of documents with field",
      "details": []
    }
  ]
},

问题在于我的集群中绝对没有29298个文档。通过以下命令确认，实际仅存在983个文档：

curl 'https://xxxxxx/_cat/count?v=true'

epoch      timestamp count
1677353551 19:32:31  983

根据IDF的定义，N应为总文档数。此外，集群中已删除的文档数量极少：

curl 'https://xxx/_cat/indices?v=true'
health status index     uuid                   pri rep docs.count docs.deleted store.size pri.store.size
green  open   en-us     kYD_PY9mRNm9wWsVYtNl8w   3   2         12            5    520.3kb        173.4kb
green  open   ds-en-us  OmhX5FMgRTqOCXQEZUP0fA   3   2        141           32        4mb          1.3mb
green  open   .kibana_1 bxMRa2KEQc2Scl3r9dUsfQ   1   1          1            0       10kb            5kb
green  open   en-gb     Ao6rToHPRmmx9LJx3HI0LQ   3   2         73           13      1.3mb        336.6kb
green  open   ds-en-gb  SOhhP4-kQ9iK8niSI_paOg   3   1        753           34    817.5mb         13.5mb

有人知道这一异常情况的原因吗？感谢解答！

内容的提问来源于stack exchange，提问作者codeedoc