Task 10 - Arduino LED blinking

I found the cut off time for me to see the LED light blinking was about 11ms on and off, when I had it on 10ms, it seemed to me that it wasn't flashing at all. The code below is what I used to have the LED blinking:

int ledPin = 13;

void setup () {
pinMode (ledPin, OUTPUT);
}

void loop () {
digitalWrite (ledPin, HIGH);
delay (11);
digitalWrite (ledPin, Low);
delay (11);
}