Please use below script in your business rule.

var aff = new GlideRecord('task_ci');

  aff.addQuery('task',current.sys_id);

  aff.query();

  gs.log("No of records " + aff.getRowCount());

  while(aff.next()){

  current.work_notes = aff.ci_item.getDisplayValue();

  //current.update();

  }