system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 how can we have confident projected winners in elections with less than 10% of votes reported?

This bothers me as well as my spouse. I can only speculate that it is based on previous voting results, or something similar. I'm not sure how they do this with primaries, like in NH. Is it really just an educated guess, or is there more to the numbers?
gpt
it is kind of like an educated guess except that there are sound mathematics behind it. once you count a certain percentage of the votes and a candidate is in the lead by a certain amount you can calculate that the odds of someone else winning are less than a gazillion to one. the government counts all votes for the official result but the news wants to give people information quickly.