When walking on treadmil
The manual calibration allows only to enter LOWER number than measured
But in fact it is higher
How can i calibrate to a higher value
ovekvam is correct. Somewhat regular GPS activities will improve the accuracy of your treadmill distance, so the calibration in smaller amounts. Please see the "Tips to Further Improve Accuracy" section of the FAQ below:
How Does the Treadmill Calibration Feature Work on My Garmin Watch?