You must specify the PXE device's altitude above sea level if a Raritan differential air pressure sensor is attached. This is because the device's altitude is associated with the altitude correction factor. See Altitude Correction Factors.
The default altitude measurement unit is meter. You can have the measurement unit vary between meter and foot according to user credentials. See Setting Up Your Preferred Measurement Units.
Note: The PDU folder is named "my PX" by default. The name can be customized. See Naming the PDU.