Actually, you'll have three different fabrics of which you'll cut 40 squares from each for a total of 120 squares. That's if we have 40 participants. If we have 20 participants, you would cut 20 squares from each of your three fabrics for a total of 60 squares. You will receive as many squares as you send and they will all be different prints.
I hope that is clearer. Let me know if it's not. :D