Would it not be more accurate to say that 15:25 was a p2 and 15:40 was a p3 but the pace accel to 15:45/15:50 signalled a new p2 at 15:50 which then led to a new p3 at 16:15? Of course, the ob at 15:40 was a bonus indication that a new p2 was on its way.