Making the first pleat (actually the edge of the front apron going INTO the first pleat) deeper than the others helps to "keep the shape" of the front apron. If there are 2 pleats, side by side and you start to expand them, the shallower pleat will expand first.

Also, Robert is right about reversing the last pleat. If the front apron is sewn down as far as the other pleats, the last pleat needs to be reversed.