is any parameter we can configure for the trend of Demantra engine forecast

Hi,

in the case we ran system forecast, it seems the trend following last 3 months, I understand that  there is a drop in last 3 months, so forecast will follow the same,  if we take a average, forecast is a little bit lower than history. is there any way we can configure forecast to refer the trend of a longer period, say 6 months, so the forecast trend will more closer to the history, In the case we use 2 years history in a weekly instance.