The purpose of using a trend factor with the forecast is to use history information to make out a trend to use. By looking back in time, you determine any trend of how the demand have been deployed. This trend is be used along with the forecast you enter.
You may also adjust the trend by setting a range of to what degree the trend will be applied. The range is set by entering values in the Trend fact min and Trend fact max fields in 'Forecast Method. Open' (FCS300/F).
In 'Forecast Method. Open' (FCS300/F), set the parameter Extrapolate with trend to 1 (using trend factor) for the forecast method to use.