The numbers at the top correspond to the value of the squares based on their columns, which are added up and shown on the right. The numbers on the left correspond to the value of the squares based on their rows, which are added up and shown on the bottom/ The square is only counted if it's full, and not if it is empty. You need to figure out a way to satisfy all the values. Press space to check your answer.
Click a square to mark it as full, click it again to mark an X at it. X and an empty square both count for an empty square, so it is just to help you know which squares are definitely empty. If you change your mind, click the X again to revert it back to empty. Note: There is a bug in the game where there can be multiple solutions for one puzzle. This doesn't happen very often, but it can be frustrating when all the values add up, but it's still wrong. I'll fix it as soon as I can.