[AlexCooper]

Universe, да есть такая трабла, так же как и c setInterval. Потому лучше использовать свой обработчик к примеру на ENTER_FRAME проверяющий время.
Возможно попробуйте setTimeout
Проверил setTimeout, тот же результат.

Добавлено через 23 минуты
setTimeout

import flash.utils.setTimeout;
 
var time:Number = -10;
 
var startTime:Number = new Date().time;
var timeLast:Number = 0;
 
timeEvent();
 
function timeEvent():void {
 
	time += 10;
 
	var colaps:Number = new Date().time-startTime;
 
	var realTime:Number = Math.floor(colaps/100)/10;
 
	if (Math.floor(realTime)!=timeLast) {
		timeLast = Math.floor(realTime);
		trace('setTimeout: '+Math.floor(time/100)/10+' RealTime: '+realTime);
	}
 
	setTimeout( timeOut, 10 );
}

setTimeout: 0.4 RealTime: 1
setTimeout: 0.9 RealTime: 2
setTimeout: 1.4 RealTime: 3
setTimeout: 1.8 RealTime: 4
setTimeout: 2.3 RealTime: 5
setTimeout: 2.8 RealTime: 6
setTimeout: 3.3 RealTime: 7
setTimeout: 3.8 RealTime: 8
setTimeout: 4.2 RealTime: 9
setTimeout: 4.7 RealTime: 10

setInterval

import flash.utils.setInterval;
 
var time:Number = -10;
 
var startTime:Number = new Date().time;
var timeLast:Number = 0;
 
setInterval( timeEvent, 10 );
 
timeEvent();
 
function timeEvent(event:*=null):void {
 
	time += 10;
 
	var colaps:Number = new Date().time-startTime;
 
	var realTime:Number = Math.floor(colaps/100)/10;
 
	if (Math.floor(realTime)!=timeLast) {
		timeLast = Math.floor(realTime);
		trace('setInterval: '+Math.floor(time/100)/10+' RealTime: '+realTime);
	}
 
}

setInterval: 0.4 RealTime: 1
setInterval: 0.9 RealTime: 2
setInterval: 1.4 RealTime: 3
setInterval: 1.8 RealTime: 4
setInterval: 2.3 RealTime: 5
setInterval: 2.8 RealTime: 6
setInterval: 3.3 RealTime: 7
setInterval: 3.8 RealTime: 8
setInterval: 4.2 RealTime: 9
setInterval: 4.7 RealTime: 10