The selected two-factor output in

The formula is the admitted two-factor output, not an element produced by a newly defined quantum product on ${\mathcal{P}}_{\Sigma }$. In the full triangle there are instead two insertion minus signs, one from $B_f$ and one from $B_{f^{\prime }}$, and their product is $+1$. Thus the partial sign $-2$ and the positive assignment factor in VII-D are consistent.