Graham specifically prescribes Book Value for Defensive investors, and Net Tangible Assets for Enterprising investors.
Therefore, the prices for Defensive quality stocks (or Graham Numbers) on GrahamValue are calculated using Book Values; and the prices for Enterprising quality stocks (or Serenity Numbers) are calculated using Net Tangible Assets.
Note: The subject is discussed in more detail in the forum topics, Defensive Investor Questions and TBVPS.