Hi Nicola
Apologies I am not so technical – I have attached a screenshot from tradingview and also the following explanation.
There are 3 candles forming the reversal
The penultimate candles comes before the reversal candle (lower low or higher high)
For a downtrend reversal The 3cr is completed when the candle after the reversal candle breaks the high of the penultimate candle.
The actual indicator draws a line on the high of the penultimate candle and also identifies the trigger candle with an icon (see attachments).
Not sure is this is enough info – but thanks for reading .
Regards – Damian