The number of candles to look back is 10 by default, but can be changed in the indicator settings.
The red line indicates the number of red candles, while the green line shows the number of green candles.
In true TradingView spirit, the author of this script has published it open-source, so traders can understand and verify it. Cheers to the author! You may use it for free, but reuse of this code in a publication is governed by House Rules. You can favorite it to use it on a chart.