Hi Dario,
I can answer your question for you. Suppose your account is Long 1.0 lots. In other words, you will profit if the market moves higher. Now suppose you get a sell signal your long position of 1.0 lot will be reduced to 0.5 lots. So even though you got a sell signal your account will still be long 0.5 lots. The reason why you would want to do this is that you believe the long-term trend of the market is up but you want to reduce your long position during pullbacks so your account does not have a significant drawdown. Of course, there is a negative to reducing lot size during drawdowns. Following the pullback, the market could possibly move significantly higher before the EA provides another buy signal to add 0.5 lots to bring your overall lot size back up to the original lot size.
Be sure to test the strategy on a demo account until you feel confident with how the EA works before moving to a live account.
Hope this helps!
Alan,