It's normal for there to be a 5% difference in humidity levels between dehumidifiers. The sensor in the 20L dehumidifier is located within the unit and is unable to be seen, so please try putting the hygrometer as close to the dehumidifier as possible. If there's a difference of over 5%, there's a possibility that the sensor has been damaged in transit. So we can assist you, please send pictures and your order number to our Customer Care Team.