Calibration should be simple enough - you will need an accurate multimeter, just take a reading of the pack and enter the real value on the web page - the software calculates the correct multiplier/offset for you.
Give it 5 mins to settle down and then check both onscreen values and multimeter. I doubt the readings are out by too much.
On the 710 issues, you may have had a bad batch if you brought from AliExpress and the like, I’ve seen it before where reject chips are sold off.