The sizes you've given don't seem consistent with any method of making HST's for a 2.5" finished block. However, if you're meant to be using the HST method where you make 4 at a time by sewing all around the edges of the squares and then slicing diagonally twice, then the 3.25" squares would result in four 2-inch finished blocks. Using the method where you make 2 HST's at a time, the 3.25" square is too small to make a finished 2.5" block and much too large for a finished 2" block. (It is just right to make a 2.25" finished block with just a little trimming.)