Max aggregation adding decimals

[Anabella_Cristaldi (Anna)]

Hi,
I'm doing a very simple aggregation, but I do not understand the results
I have 4 documents with a numeric field value called risk_score with values 0, 5, 4 and 6.4
When I perform a max aggregation

GET index-2019-07/_search
{
  "size":0,
  "query": {
    "term": {
      "asset": {
        "value": "IBM_server"
      }
    }
  }, "aggs" : {
        "max_risk" : { "max" : { "field" : "risk_score" } }
    }
  }

I get the following value

    {
      "took" : 0,
      "timed_out" : false,
      "_shards" : {
        "total" : 1,
        "successful" : 1,
        "skipped" : 0,
        "failed" : 0
      },
      "hits" : {
        "total" : {
          "value" : 4,
          "relation" : "eq"
        },
        "max_score" : null,
        "hits" : [ ]
      },
      "aggregations" : {
        "max_risk" : {
          "value" : 6.400000095367432
        }
      }
    }

Is it correct that returns 6.400000095367432 instead of returning 6.4?

I put some script in the table I need to display the value (using an script i n the JSON input) in order to round, but I would linke to understand why is displaying such a value

Thank you
Regards