  Let $\Delta$ be a $3$-dimensional lattice polytope containing exactly one
interior lattice point. We give a simple combinatorial formula for computing
the stringy $E$-function of the $3$-dimensional canonical toric Fano variety
$X_{\Delta}$ associated with the polytope $\Delta$. Using the stringy
Libgober-Wood identity and our formula, we generalize the well-known
combinatorial identity $\sum_{\theta \preceq \Delta \atop \dim (\theta) =1}
v(\theta) \cdot v(\theta^*) = 24$ holding in the case of $3$-dimensional
reflexive polytopes $\Delta$.
