PUT _ingest/pipeline/enrich
{
  "processors": [
    {
      "enrich": {
        "description": "Add Events to customer",
        "policy_name": "merge",
        "field": "contact_id",
        "target_field": "events",
        "max_matches": "128"
      }
    }
  ]
}

I am not able to increase the max_matches value. Please help me how to increase this value?