Out of a yard of fabric you will probably get 56 squares at most, less if your fabric is not cut square. (I'm figuring 8 5" squares across the width of the fabric and 7 down the length, 8*7=56.)
So if you're using 9 fabrics, one yard each, 5" squares, you will wind up with 56 D9P blocks that measure 13" finished. If you put them in a configuration of 8x7 blocks you will wind up with a quilt that is 104 x 91. This is a little smaller than what you want, so you may want to add borders, or make more blocks. The person who wrote the tutorial used 6" squares, which would finish at 16" per D9P block, but I find it confusing that she doesn't sew the block back together right after it is cut into 4 pieces, but instead appears to work with the 4 individual pieces when making her rows. (Am I reading the directions wrong?) All the other directions I've seen have you sew the 4 pieces back right away, and I think that is an easier way of approaching the D9P.