校正出来ました。
英文説明書の小さな字を解読したところ、校正方法が載っていました。
7. Calibrating Operation:
Press the button "ON/OFF" for 3 seconds till the screen displays a weight(for example:500.0). please put right calibration weights(500G) on the salver (If you do not;have right calibration weights,you can press the button "TARE" to select a weight) ,you can see the data on the screen Is changing ,then displays"PASS" and the back light become bright .
The calibrating operation is complete ,(You should calibrate the scale when the temperature change or other other reasons).
Press the button "ON/OFF" for 3 seconds till the screen displays a weight(for example:500.0). please put right calibration weights(500G) on the salver (If you do not;have right calibration weights,you can press the button "TARE" to select a weight) ,you can see the data on the screen Is changing ,then displays"PASS" and the back light become bright .
The calibrating operation is complete ,(You should calibrate the scale when the temperature change or other other reasons).
基準にしたF1級200ｇの公差が±0.001ｇでM2級（天秤用）200ｇの公差が±0.03ｇなので、50ｇまでは良いのですが
M2級20ｇの公差は±0.008ｇ、10ｇは±0.006ｇなのでこの辺は微妙ですね。