say you had $100 of a portfolio. Your # of futures contracts needed to hedge that portfolio =
hedge Ratio = (Duration of Portfolio * Value of Portfolio)/(Duration of Futures contract * Price of futures contract) * Conversion Factor for CTD bond.
Price of futures contract which is on the denominator is what we are discussing with the projected basis value.
If that futures value is higher than the actual value - your hedge ratio is lower than what is actually needed. So you are going to be actually hedging for your $100 portfolio with fewer futures contracts than you actually need.