Documentation improvement.

README.md

@@ -77,7 +77,7 @@ In order to avoid/minimize the unnecessary change of fan levels the service empl
 
  1. When the service adjusts the fan rotational speed then it always applies a delay time defined in configuration parameter `[IPMI] fan_level_delay=` in order to let the fan implement the physical change.
  2. There is a sensitivity threshold parameter (`sensitivity=`) for the fan control logic. If the temperature change is below this value then the service will not react at all. 
- 3. There configuration parameter `polling=` can also impact the frequency of change of the fan levels. The bigger polling time in a zone the lower frequency of changing of the fan speed.
+ 3. The configuration parameter `polling=` defines the frequency of reading zone's temperature. The bigger polling time in a zone the lower frequency of fan speed change.
 
 #### 3. Swapped zones
 In some cases it is useful to swap IPMI zones. In this way the fans `FAN1, FAN2, ...` will cool the HD zone and the fans `FANA, FANB, ...` will cool the CPU zone. This feature could be useful if you need more fans for the HD zone since Super Micro motherboards have more fan connectors in the CPU zone usually. This feature can be enabled with `[IPMI] swapped_zones=True` configuration parameter, in default it is disabled.