Merlin HM9 Manuel D'utilisation page 73

Operation
Density specifications can differ depending
on the location. In this case, the wood type
must be selected according to the actual dry
density.
Type classifications are recommendations for
standard settings. In some cases, a correction
of the setting of +/- 1 is necessary for core
material (+1) or side cut material (-1) due to
varying density.
72
Wood moisture meter