LAS VEGAS (NewsNation) — The odds of picking a perfect March Madness bracket are 1 in 9.2 quintillion. While you let that number rattle around in your brain, let’s discuss how oddsmakers go about setting betting lines to go with all those games.

Bear in mind that heavy underdog St. Peter’s upset powerhouse Kentucky in Thursday’s first-round games and you’ll understand why the life of an oddsmaker is a lot like the life of a weatherman: You assemble all the facts and you make your prediction, but chaos theory always has a hand in the outcome.

NewsNation’s Alex Caprariello is in Las Vegas for the tournament, and he talked to some oddsmakers about how they do the voodoo that they do. He learned that there’s a balance between setting a line that’s attractive to bettors while not going overboard and giving away the house.

The process of setting odds at Westgate Sportsbook, one of the powerhouses of Vegas sports betting, began months ago, with oddsmakers scrutinizing teams’ offense and defense, coaching decisions, team speed and much more to come up with power rankings. They built a picture of each team and then, when the bracket is set, the matched those pictures up against each other to set the odds.

As teams are knocked out of the tournament, the analysts feverishly scribble away and set the odds for the next round. Jay Kornegay, with Westgate, said, “Most of the time we’re spot-on, and other times we might be off by a couple here and there, but we have a lot of confidence in our numbers.

The importance of those numbers comes into clear focus when you realize that Americans will bet $3.1 billion on March Madness. According to Yahoo Sports, only 14% of brackets are still intact, especially thanks to the Kentucky game, so expect the oddsmakers’ pencils to be giving off sparks.