The valuation percentage shows how far above or below its current price the stocks historical valuation is. It takes into account a long-term average of the Price to Sales Ratio and Price to Earnings Ratio and mathematically determines whether the current price is high or low relative to those historic valuation multiples.
A negative value indicates the current price is above the historical valuation while a positive value indicates it is currently trading at a discount to the historical valuation.
It is important to note that this is not a measurement of how the stock's price relates to its "intrinsic value", but is instead a measurement of how the market is valuing the stock relative to how it was valued historically.
Valuation Percentage = [Valuation (Historical Mult.) - Current Stock Price] / Valuation (Historical Mult.)
See the Valuation (Historical Mult.) link in the Related Terms section for more information on its calculation.