Applying filters in Sensu

Question

I have tried applying a filter in Sensu, from referring Sensu document, for reducing our monitoring alerts. But problem is, this filter is sending email only when issue is in Resolved state, no critical or warning alerts. Filter looks like :

{
  "filters": {
    "state_change_only": {
      "negate": false,
      "attributes": {
        "occurrences": "eval: value == 1 || ':::action:::' == 'resolve'"
      }
    }
  }
}

Please help me in understanding this behaviour and what this eval: value == 1 actually means here.

Does it have to do anything with occurrences value? I have values like 2,3 etc. depending on the severity of the checks.