Awol,
It is to my limited understanding of C++/C programming that would say in my humblest opinion that the interval only set the duration between how long it will turn on/off.
lets say that i change the interval to 2000
it would mean that the led will turn on for 2 second and then turn off for 2 second and the cycle will repeat it self.
what I'm trying to achieve now is to turn the led on for maybe 3 second and then off for maybe 5 second.
I hope that my explanation is correct and I will be glad if I'm wrong cause only then i could improve my understanding and my self as a whole.