Graham Number is named after the “father of value investing,” Benjamin Graham, who was a mentor of Warren Buffett. The figure takes into account earnings per share and book value per share to measure a stock's maximum fair market value. In other words, it is the upper end of the price range that a defensive investor should pay for the stock.
The Graham Number = Square Root of (22.5) x (tmm EPS) x (mrq Book Value per Share).
The 22.5 is included in the formula as a rule of thumb to account for Graham's assumption that the price-to-earnings ratio should not be over 15 and the price to book ratio should not be over 1.5 for an undervalued stock. So, the number is generated as (P/E of 15) x (P/B of 1.5) = 22.5.
So the script generates a Graham number plot.