A hedge ratio determines the amount of par of the hedge position that needs to be bought or sold for every $1 par value of the original position. The goal of hedging is to lock in the value of a position even in the face of small changes in yield. The hedge ratio is given by:

$$\text{HR} = \frac{\text{DV01 of initial position}}{\text{DV01 of hedging tool}} = \frac{0.18125}{0.11369} = 1.59$$

Interpretation: For every $100 par value of the 20-year bond, short $159 of par of the 10-year bond.