4 categories (ex. price, drink, food, person)
4 in each category (ex. $4, $5, $6, $7)
Only the top row matters, but the other 3 boxes are there to help you figure out what's what by placing the Xs and Os.
You can click the clues on the right side to eliminate them when you don't need them anymore, and there's a tab right above where it says "active clues" called "notes" where you can write down things should you need to.
But if you think the 4x4 is a monster, check 4x7! (4 categories, 7 options in each category)