window.onload = function() 
{ 

	document.getElementById('id-6EA13C2F-E50C-04B0-B508-596D6FCD6A0C').onkeypress = function() 
	{
    var sub=this.value.length;
  
    	if (sub < 300) 
    	{
       document.getElementById('id-92EB2097-D493-AF56-933F-1723592BBDFE').value= (299 - sub);
    	}

    	if (this.value.length >= 300) 
    	{
    	  this.value = this.value.substring(0,299);
    	  alert('Only 300 characters are allowed');
    	}
	}

}