The rules of Chomp are simple. The first player chooses one spot on the board and removes all squares that are at least as high and at least as far right as it (i.e., all squares for which both coordinates are greater than or equal to the corresponding coordinates of the chosen square). The goal is to avoid having to eat the poison square (i.e., you don't want it to be your turn when only the ☠️ square is left). Manifold is be Player 1, and Player 2 is a computer player. The board started as a 4x7 grid, as seen below:

On Move 1, Manifold played (3,4), and the computer responded with (2,6), so the board now looks like this:

Which square should be selected for the second move? Out of all the answers that express valid moves, the top three will be selected as contenders when the market closes. Then I'll make conditional markets asking whether Manifold will win, given that each contender is chosen, and chose the move that has the highest average probability in the conditional markets. This will continue until the game ends.

If you're confused about the rules, here's the wikipedia article on the game: 

Note that Wikipedia uses a different convention where the poison square is in the top-left instead of the bottom-left, so its rules are vertically flipped relative to ours.