The 'Two Point Values' used to calibrate ADC readings, unlike 'eFuse Vref', are not measured and burned into eFuse BLOCK3 for each individual chip during factory calibration. This operation should be done by user, if more accurate calibration is required.

docs/en/api-reference/peripherals/adc.rst

@@ -114,7 +114,7 @@ Calibration Values
 
 Calibration values are used to generate characteristic curves that account for the unique ADC reference voltage of a particular ESP32. There are currently three sources of calibration values. The availability of these calibration values will depend on the type and production date of the ESP32 chip/module.
 
-**Two Point** values represent each of the ADCs’ readings at 150mV and 850mV. These values are measured and burned into eFuse ``BLOCK3`` during factory calibration.
+**Two Point** values represent each of the ADCs’ readings at 150mV and 850mV. To obtain more accurate calibration results these values should be measured by user and burned into eFuse ``BLOCK3``.
 
 **eFuse Vref** represents the true ADC reference voltage. This value is measured and burned into eFuse ``BLOCK0`` during factory calibration.