Behaviour-of-RisingFalling-Indicator

I don't understand the behaviour of RisingFalling Indicator in this case:

Why is the (IndicatorBase) cast necessary?

CODE:
public class MyStrategy : UserStrategyBase
    {
      //Deere (DE) 22.04.2024 - 03.05.2024
      
        //create indicators and other objects here, this is executed prior to the main trading loop
        public override void Initialize(BarHistory bars)
        {               
         TimeSeries indicator = new SMI(bars, 20);

         TimeSeries smoothedIndi = new Gaussian(indicator, 13, 2);
         PlotTimeSeries(smoothedIndi, "smoothedIndi", "3", WLColor.Green);
         RisingFalling rs2 = new RisingFalling(bars, (IndicatorBase)smoothedIndi, HistoryScale.Daily);
         PlotTimeSeries(rs2, rs2.Name, "4", WLColor.Black);
         
        }

        //execute the strategy rules here, this is executed once for each bar in the backtest history
        public override void Execute(BarHistory bars, int idx)
        {
        }
    }

Examples:
Why is on 27.02.2024 the indicator -1?
Why is between 18.04.2024 and 22.04.2024 the indicator +1?