Calculator display

I am working on building a calculator. following a tutorial on sayweb. I am trying to input the numbers into the display field using the following code:

import flash.events.MouseEvent;
var btn:Array = new Array();
for(var i = 0; i < 10; i++) {
          var myBtn:Btn = new Btn();
          myBtn.y = 15;
          myBtn.x = i * 100 + 15;
          myBtn.width = 48;
          myBtn.height = 48;
          myBtn.buttonMode = true;
          myBtn.mouseChildren = false;
          myBtn.caption.text = String (i);
          addChild(myBtn);
          btn.push(myBtn);
}
btn[0].y += 370;
btn[0].x += 10;
btn[1].y += 310;
btn[1].x += -90;
btn[2].y += 310;
btn[2].x += -130;
btn[3].y += 310;
btn[3].x += -170;
btn[4].y += 250;
btn[4].x += -390;
btn[5].y += 250;
btn[5].x += -430;
btn[6].y += 250;
btn[6].x += -470;
btn[7].y += 190;
btn[7].x += -690;
btn[8].y += 190;
btn[8].x += -730;
btn[9].y += 190;
btn[9].x += -770;
//OPERATORS//
var operators:Array = new Array();
for(var io:int = 0; io < 10; io++) {
          var opBtn:Btn_operator = new Btn_operator();
          opBtn.width = 48;
          opBtn.height = 48;
          opBtn.buttonMode = true;
          opBtn.mouseChildren = false;
          opBtn.caption_op.text = String (".");
          addChild(opBtn);
          operators.push(opBtn); 
}
operators[0].y += 383;
operators[0].x += 78;
operators[0].caption_op.text = String(".");
operators[1].y += 383;
operators[1].x += 138;
operators[1].caption_op.text = String("=");
operators[2].y += 383;
operators[2].x += 198;
operators[2].caption_op.text = String("/");
operators[3].y += 323;
operators[3].x += 198;
operators[3].caption_op.text = String("*");
operators[4].y += 263;
operators[4].x += 198;
operators[4].caption_op.text = String("-");
operators[5].y += 203;
operators[5].x += 198;
operators[5].caption_op.text = String("+");
operators[6].y += 263;
operators[6].x += 256;
operators[6].caption_op.text = String("-/+");
operators[7].y += 323;
operators[7].x += 256;
operators[7].caption_op.text = String("C");
operators[8].y += 383;
operators[8].x += 256;
operators[8].caption_op.text = String("CE");
operators[9].y += 203;
operators[9].x += 256;
operators[9].caption_op.text = String("<-");
display_txt.text = "0";
var numberEntered:String ="";
//VARIABLE HANDLE OPERATION NOT BUTTON
var operate:String;
//HANDLE FIRST AND SECOND VALUE
var num1:Number;
var num2:Number;
//grouping all buttons in function
function addListeners():void{
          for (var n:uint=0; n < btn.length; n++){
                    btn.addEventListener(MouseEvent.CLICK,pressNumber);
          }
          for (n=0; n < operators.length; n++){
                    operators.addEventListener(MouseEvent.CLICK,pressOperator);
          }
          operators[8].addEventListener(MouseEvent.CLICK,clearAll);
          operators[0].addEventListener(MouseEvent.CLICK,addDot);
  
}
function pressNumber(event:MouseEvent):void{
          //FIND NAME OF BUTTON PRESSED
          var instanceName:String=event.target.name;
  
          var numPushed = instanceName.charAt(4);
  
if (display_txt.text == "0"){
          //REMOVE 0 FROM SCREEN
          display_txt.text ="";
}
          display_txt.appendText(numPushed);
}
  
function pressOperator(event:MouseEvent):void{}
function clearAll(event:MouseEvent):void{}
function addDot(event:MouseEvent):void{}
addListeners();

Here is the code im using to input:

function addListeners():void{
          for (var n:uint=0; n < btn.length; n++){
                    btn.addEventListener(MouseEvent.CLICK,pressNumber);
          }
          for (n=0; n < operators.length; n++){
                    operators.addEventListener(MouseEvent.CLICK,pressOperator);
          }
          operators[8].addEventListener(MouseEvent.CLICK,clearAll);
          operators[0].addEventListener(MouseEvent.CLICK,addDot);
  
}
function pressNumber(event:MouseEvent):void{
          //FIND NAME OF BUTTON PRESSED
          var instanceName:String=event.target.name;
  
          var numPushed = instanceName.charAt(4);
  
if (display_txt.text == "0"){
          //REMOVE 0 FROM SCREEN
          display_txt.text ="";
}
          display_txt.appendText(numPushed);
}

However in the display area it doesn't output the right numbers, but characters. so when charAt(4) it outputs 'a' and when its at charAt(3) it outputs 't'