Question about percentile rank query

[Nee_Defeng]

I had this query, with which I would expect to have value '0.000005' below the value returned from the record

              "system" : {
                "pct" : 0.016}

The question is: why it still shows the percentile as 100.0?

GET /metricbeat-7.3.1/_search
{
  "aggs": {
    "test_percentile": {
      "percentile_ranks": {
        "field": "system.cpu.system.pct",
        "values": [
          1,
          0.5,
          0.000005
        ]
      }
    }
  }, 
  "query": {
    "bool": {
      "filter": {
        "match": {"_id": "cKdA9mwBa9ZjV3C_Jg5w"}
      }
    }
  }
}

And the response was:

{
  "took" : 432,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 1,
      "relation" : "eq"
    },
    "max_score" : 0.0,
    "hits" : [
      {
        "_index" : "metricbeat-7.3.1",
        "_type" : "_doc",
        "_id" : "cKdA9mwBa9ZjV3C_Jg5w",
        "_score" : 0.0,
        "_source" : {
          "@timestamp" : "2019-09-03T08:31:34.025Z",
          "ecs" : {
            "version" : "1.0.1"
          },

......
"id" : "a43e1577a5804785a131ba4d1ef34ea3",
"containerized" : false
},
"agent" : {
"id" : "cb4997de-b548-4ea4-9a48-9ab8fbb9dabe",
"version" : "7.3.1",
"type" : "metricbeat",
"ephemeral_id" : "5cbbd81b-0b97-41ac-9adb-8062b73459e4",
...... },
"event" : {
"module" : "system",
"duration" : 262779,
"dataset" : "system.cpu"
},
"metricset" : {
"name" : "cpu"
},
"service" : {
"type" : "system"
},
"system" : {
"cpu" : {
"softirq" : {
"pct" : 0.001
},
"system" : {
"pct" : 0.016
},
"cores" : 8,
"nice" : {
"pct" : 0
},
"total" : {
"pct" : 0.032
},
"iowait" : {
"pct" : 0
},
"irq" : {
"pct" : 0
},
"user" : {
"pct" : 0.015
},
"idle" : {
"pct" : 7.968
},
"steal" : {
"pct" : 0
}
}
}
}
}
]
},
"aggregations" : {
"test_percentile" : {
"values" : {
"5.0E-6" : 100.0,
"0.5" : 100.0,
"1.0" : 100.0
}
}
}
}