This indicator was written in order to apply bar limit in strategies and it was published as open code so that everyone can use it. When backtesting with stock market api data, we determine how many bars should be, not from which date the data will be drawn. For example, we can draw 1000 bar data from stock exchange and perform the backtest on this data. You can plan your strategy by checking the number of bars you test with the window () == 1 parameter here while checking through Tradingview to check that the test we performed gives correct results.