I'll use the example above to show you how to make the strategy more clear.
As you see from the Minev's screenshot, the strategy opens Up positions when the bar opens below the Upper Band.
Because the app sets automatically mirrored rules for Down positions, it will open Down when the bar opens above the Lower Band.
If you read the above carefully, you will notice that if the bar opens between the Upper and the Lower band, both Up and Down trading rules are satisfied. Fortunately, the app detects such cases and will not produce a trade.
The strategy will open Up only if the bar opens below the Lower Band because only the Up rule will be satisfied.
Having that in mind, we can safely change the Bollinger Band rule to "The bar opens below Lower Band".
That will not change the strategy result, but will make it more clear.
With that change it will be easy to understand that the strategy uses the Bollinger bands to detect overbought and oversold conditions and trade in the opposite direction.