Ffmpeg process field - Recording with ffmpeg what to enter is stop recording

Thanks for ghe reply @Yoichi. What is the reason. Is it just creating a reference as to which start recording is being stopped?

Is there significance in the letter p have chosen? Eg does p stand for something… or could you have just as effectivly chosen another letter such as z?

Do i set it by just typing the letter p in both, or is it actually a ctl K to set / define.