In theory this can be used to screen for over- and undervalued stocks, however as Graham himself notes, you should look into other fundamentals when using them in conjunction with Grahams formula.
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.