[RyDeR`]

Top of the script;

Code:

new CountDownFromAmount;
forward CountDownTimer();

OnGameModeInit;

Code:

CountDownFromAmount = 480; // 8min.
SetTimer("CountDownTimer", 999, 1);

Somewhere in you're script;

Code:

public CountDownTimer()
{
	CountDownFromAmount--;
	if (CountDownFromAmount == 0)
	{
		GameTextForAll("End of round!!", 3000, 5);
	}
	return 1;
}

Edit: Use format and GameText to see the counting.