OZONE GAS SENSOR 12-BIT

Hi. I bought to OZONE GAS SENSOR 12-BIT.
The data sheet says measurement up to 0-20 ppm. We have 400 ppm of ozone coming out of the ozone generator. But I don’t know why it’s coming down. Like 0.078ppm->0.005ppm.
The sensors were heated 24 hours.
Hardware configuration is Arduino Uno + Arduino Uno Compatible I2C Shield + Ozone Gas Sensor 12-Bit (MQ131)

//
/*
Distributed with a free-will license.
use any of them
ADC121C_MQ131
This code is specified to work with the ADC121C_I2CGAS_MQ131 I2C Mini Module available from ControlEverything.com.
https://shop.controleverything.com/products/ozone-gas-sensor-12-bit
NT.
*/
/
/

#include <Wire.h>
#include <ADC121C_MQ131.h]

ADC121C_MQ131 mq131;

void setup (void)
{
Serial.Begin(9600);

The address can be changed the option of connecting multiple devices
mq131.getAddr_ADC121C_MQ131(ADC121C_MQ131_DEFAULT_ADDRESS); // 0x50, 1010000
// mq131.getAddr_ADC121C_MQ131(ADC121C_MQ131_ADDRESS_FLGND); // 0x51, 1010001
// mq131.getAddr_ADC121C_MQ131(ADC121C_MQ131_ADDRESS_FLVA); // 0x52, 1010010
// mq131.getAddr_ADC121C_MQ131(ADC121C_MQ131_ADDRESS_GNDFL); // 0x54,10100
// mq131.getAddr_ADC121C_MQ131(ADC121C_MQ131_ADDRESS_GNDGND); // 0x55, 10101
// mq131.getAddr_ADC121C_MQ131(ADC121C_MQ131_ADDRESS_GNDVA); // 0x56,1010
// mq131.getAddr_ADC121C_MQ131(ADC121C_MQ131_ADDRESS_VAFL); // 0x58, 1011000
// mq131.getAddr_ADC121C_MQ131(ADC121C_MQ131_ADDRESS_VAGND); // 0x59, 1011001
// mq131.getAddr_ADC121C_MQ131(ADC121C_MQ131_ADDRESS_VAVA); // 0x5A, 1011010

// The Automatic Conversion Mode, Alert Hold, Alert Flag Enable,
// Alert Pin Enable and ALERT Pin Polarity
can be changed via the following features

mq131.setCycleTime (CYCLE_TIME_32); // Tconvert x 32, 27 ksps
// mq131.setCycleTime (AUTOMATIC_MODE_DISABLED); //automatic mode disabled, 0 ksps
// mq131.setCycleTime (CYCLE_TIME_64); // Tconvert x 64, 13.5 ksps
// mq131.setCycleTime (CYCLE_TIME_128); // Tconvert x 128, 6.7 ksps
// mq131.setCycleTime (CYCLE_TIME_256); // Tconvert x 256, 3.4 ksps
// mq131.setCycleTime (CYCLE_TIME_512); // Tconvert x 512, 1.7 ksps
// mq131.setCycleTime (CYCLE_TIME_1024); // Tconvert x 1024, 0.9 ksps
// mq131.setCycleTime (CYCLE_TIME_2048); // Tconvert x 2048, 0.4 ksps

mq131.setAlertHold(ALERT_HOLD_CLEAR); //Alerts will self-clear
// mq131.setAlertHold(ALERT_HOLD_NOCLEAR); //Alerts will not self-cleared