The directions don't say what size the finished quilt is. But there are 24 squares that finish at 1.5" in each direction. So, 24 x 1.5" = 36". Then there are borders added. The borders are 3 1.5" finished size squares, and there are 2 sides in each direction, so 2 x 3 x 1.5" = 9" of border, so the quilt finishes at 36" +9" = 45" x 45".
The quilt is made by making 2" strip sets, cutting them into 2" strips. Then you can sew in tubes, and unsew one color up each time, or move one square to the bottom of the strip, then 2 squares to the bottom of the strip, .... and that makes the pattern that you see.