When a strategy is running and the entry rules are satisfied the strategy rises an initial entry signal and opens a position. However, if it happens that the entry conditions are satisfied and we have already an open position the strategy acts acts as per the "Next entry signals" settings. Such additional entry signal can be either in the position direction, where the strategy can add or cancel the entry or in the opposite direction where the strategy can reduce, close or reverse the position.
The "reduce" next opposite direction signal behavior makes sense only when there is an actual opposite direction signal. If you open only long positions, the strategy will never rise a short entry signal, which makes the "reduce" option pointless.