Production line battery voltage ADC calibration scheme

The calibration method is as follows:
externally provides a fixed voltage V11, the device ADC takes the value V1; externally provides a fixed voltage V22, the device internal ADC takes the value V2; then:
V11 = Gain * V1 + Offset;
V22 = Gain * V2 + Offset;
Use the above two calculation formulas to calculate Gain and Offset;
V after correction = Gain * V acquisition value + Offset;