This indicator was originally developed by David Sepiashvili (Stocks & Commodities V. 24:2 (February, 2006): The Self-Adjusting RSI).
The author presented a technique to adjust the traditional RSI overbought and oversold thresholds so as to ensure that 70-80% of RSI values lie between the two thresholds.
He used two algorithms for adjusting:
Standard Deviation-based
Simple Moving Average-based
Easy and straightforward. But this is not a true way.