What do P1/2/3/4 means (old models only have F1/F2)?

What do P1/2/3/4 means (old models only have F1/F2)?

P1 refers to the temperature difference (corresponding to the old model F1). If you set it to 5 and the chiller is set to 47, you're going to have a 5 degree temperature difference around 47.
P2 refers to delayed start. The default delay time is three minutes. If set to 3, the chiller will start working within 3 minutes of setting the temperature.
P3 refers to temperature correction (corresponding to the old model F2). If the temperature is correct, no adjustment is necessary.
P4 means automatically turning off the screen. If set to 3, the screen will automatically turn off after 3 minutes of inactivity.