Phrase_prefix query returns empty result if I search for 3 characters but returns non-empty result if I search for 4 and more characters

Elastic Stack Elasticsearch
1

Hi,
I have this query :

"match": {
  "_all": {
    "query": "ana",
    "type": "phrase_prefix"
  }
}

This query does not return anything with phrase "ana" that is 3 characters length, but if I search for 4 characters phrase "anat" it returns result :

match": {
  "_all": {
  "query": "anat",
  "type": "phrase_prefix"
  }
}

What could be the problem here ? I have no idea why is that and how to solve this.

Thanks !!!