A:Answer Hi, Emilie!
The 15p you observed is in reference to the High Pressure setting. When you select High Pressure, the screen will display the pressure rating, which in this case means 15psi. Most recipes will call for high pressure. The pot is set to high pressure as the default, so there is usually no need to adjust the pressure setting.
However, the pressure setting can't be manually adjusted. You can select High Pressure or Low Pressure by pressing the Pressure Level button. It will cycle between High Pressure and Low Pressure, but that's all.
If you want to set the time, simply press the function you wish to use. A time will display on the screen. You then have a few seconds to press the "+" or the "-" buttons, which will adjust the time upward or downward. Bear in mind that times on the Instant Pot are displayed in hours and minutes.
