 $\tau_0({\Delta}) :=  \sum_{ k_{0,0} \le  |{\partial}\Pi | \le  k_{0,0} }  |{\partial}\Pi |$, where the summation takes place over all faces $\Pi$ in ${\Delta}$ such that $ k_{0,0} \le  |{\partial}\Pi | \le  k_{0,0}$, where $k_{0,0}, k_{0,0}$ are fixed integers with $0 \le k_{0,0} \le  k_{0,0} \le |W|$