continuous footnote rule width

hello

i am trying to make the continuous footnotes rule width 53 mm using this :

but it does not working

Main();

function Main() {

  if (app.documents.length > 0) {

  var myDoc = app.activeDocument;

        myDoc.footnoteOptions.continuingRuleWidth   ["53 mm"];

  alert("Finished!");

  }

  else {

  alert("No continuous footnotes.");

  }

}