diff --git a/fhem/FHEM/10_MAX.pm b/fhem/FHEM/10_MAX.pm
index 52ebff498..60161b3d6 100755
--- a/fhem/FHEM/10_MAX.pm
+++ b/fhem/FHEM/10_MAX.pm
@@ -885,7 +885,7 @@ MAX_Parse($$)
     <li>comfortTemperature &lt;value&gt;<br>
       For devices of type HeatingThermostat only. Writes the given comfort temperature to the device's memory. It can be activated by pressing the rightmost physical button on the device.</li>
     <li>measurementOffset &lt;value&gt;<br>
-      For devices of type HeatingThermostat only. Writes the given temperature offset to the device's memory. The thermostat tries to match desiredTemperature to (temperature = measured temperature at sensor + measurementOffset). Usually, the measured temperature is a bit higher than the overall room temperature (due to closeness to the heater), so one uses a small negative offset. Must be between -3.5 and 3.5 degree celsius.</li>
+      For devices of type HeatingThermostat only. Writes the given temperature offset to the device's memory. If the internal temperature sensor is not well calibrated, it may produce a systematic error. Using measurementOffset, this error can be compensated. The reading temperature is equal to the measured temperature at sensor + measurementOffset. Usually, the internally measured temperature is a bit higher than the overall room temperature (due to closeness to the heater), so one uses a small negative offset. Must be between -3.5 and 3.5 degree celsius.</li>
     <li>minimumTemperature &lt;value&gt;<br>
       For devices of type HeatingThermostat only. Writes the given minimum temperature to the device's memory. It confines the temperature that can be manually set on the device.</li>
     <li>maximumTemperature &lt;value&gt;<br>