Oh, I am usually really good at math, but this is making my head hurt. We also need to take into consideration the amount of sashing in between each of the blocks when figuring the size of the blocks. Based on Gayle's figures and the picture you have posted, I am thinking that the sashing shown is about 1/2" and that the blocks would then be 4 1/2".
Therefore, the 5 across the top row (the 6th is a repeat) would form a repeat and would measure 24 1/2" and the three blocks going down (the 4th is a repeat) would measure 14 1/2".