Yes ... This is a funky type swap. The sizes can all fit together like a puzzle to make a 12 1/2" block. If you look at the valentines swap tops that the girls have made, you can get an idea of how they are setting the odd sizes together.
For example if you take a 9 1/2 " square block and add a 3 1/2 by 9 1/2 to it, then add a 3 1/2 by 12 1/2 to that. You have the 12 1/2 inch square block. Many combinations work to give you a 12 1/2" block to fit them all together for a quilt top.