The pictures give a general idea of how many pieces, so how much actual stitching and cutting are involved. Every edge can mean cutting, stitching, and the bulk and weight of the fabric in the seam. Those arrows on corners, coming at the two ends of a line, mean that the edge of the pattern is butted to a fold. Eliminating seams can make the garment quicker and less complicated to sew, but less fitted. The instructions are usually inside the pattern envelope. It looks as if Jolie is supplying a picture of that envelope. You need the pieces to know the exact cutting lines.