Make sure that your room lighting doesn't change throughout this test e.g. same intensity.
Place your left hand (palm) inside the box with dotted border.
Press capture button.
Decrease precision value to a value a bit larger than shown by deviation.
Make sure that unintended, small movement of your palm is negligible and the green,
smaller than sign keeps showing. If this sign becomes red,
larger than sign , try to increase the precision value a little.