We'll be playing 10 games. So if I win 5 games, then this resolves to 50%. If I win all of them (the most likely option, surely), then this resolves to 100%. If @Conflux wins 10, then this resolves to 0%.

See also this market which asks whether @Conflux will win the majority:

And this market where @Conflux is allowed a teammate:

I will not buy any NO shares in this market, and @Conflux has agreed to not buy any YES shares.