I guess I didn't mean the seed, but the actually randomly generated number.
So the first time it produces a 40, so 40ms later, it produces a 521, 521ms later it makes, etc....
Unless I'm misunderstanding how this works overall.
But I figured, using millis to do a random blink, it would generate a random number, then loop through the code until it reaches that number, then do something, and make a new random number.