ok, so it's not like the game "I'm thinking of a random number between 1 and 10" and the other person has to guess.

in this case, the miner just needs to find some small number that produces a hash with a lot of leading "0's"

then i wondered what happens when 2 miners find the small number at the exact same time. research says that the chain forks temporarily, and the nodes resolve to the longer chain. i assume this is in the bitcoin core code that the nodes run.