That is the book by Kevin at NERD, right? I think you must be misreading it. I don't have it myself (yet!), but I find it hard to imagine he says that you can get a super cinnamon by breeding a patternless to a normal.
You are right both with your percentage and with it being a lot of luck. Those percentages are what you can expect on average, but what really happens is each egg has a 50% change of being pastel, 25% chance of being super, and 25% chance of being normal.
It is somewhat like flipping a coin. You would expect on average that you will get 50% heads and 50% tails. But really, each time you flip it, those are your chances. So it is very possible to flip a coin twice and get either both heads or both tails, instead of one of each.
So did I help or make it more confusing?