ActionScript 3.0 :: Typewriter Text Effect - String Not Displaying Completely

I'd like the words in the string to type out in the allotted time, but for some reason my function appends the first and last letter of anything in the string, so "Hello?" becomes "ello." This is not affected if I pad the text in the string with spaces, i.e. " Hello? " Nor does this work if I start count i at -1, not 0.

import flash.utils.Timer;import flash.events.TimerEvent;
var str:String = "Hello?";
var i:int = -1;var delay:int = 720%str.length;
var timer:Timer = new Timer(delay);
timer.start();
timer.addEventListener(TimerEvent.TIMER,gotime);
function gotime(e:TimerEvent){
textbox_txt.appendText(str.charAt(i));i++;
if (i>=str.length){timer.stop();}}