I'm not very familiar with how they work. Don't prediction markets give the individual gambler a boolean choice and this results in a picture of the split over the population? There's no granular option for the individual to bet 40% vs. 60% for something happening, the vote with 100% confidence that Spain wins the World Cup, they don't give 85% chance of winning.

The way to express a 85% confidence is to size your investment accordingly. For example, if the market is at 75%, then you buy yes-shares until the price is at 85%. If the market is at 90%, then buy no-shares instead until the price is down to 85%.