By default it shows Standard Deviation Percentage for 10 periods.
While price will be moving away from mean, it will be printed in green, while price will retrace towards mean, it will be printed in red.
Currently, we have indicators available to print Standard Deviation but value of standard deviation depends upon value of underlying. This indicator will show deviation from mean in terms of percentage.
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.