Press the green flag, press the space bar to set speed to the max, otherwise use the slide bar on the bottom. This is a number generator which generates a number pattern called the Fibonacci Sequence. Scroll down for more explanation on Fibonacci numbers in general. The Fibonacci series starts at 0, 1 (or sometimes 1, 1). The next number in the series is always the sum of the last two numbers. For example if the first two numbers are 1 and 1, then the next number is 2. The next number will be 3 because the last two numbers are 1 and 2. That's about it.
Whoever Fibonacci was. Me. Go check out my other projects as well! Unfortunately, Scratch can only support 1475 Fibonacci numbers until it starts listing numbers as "Infinity".