There are two types of parabolic Kazhdan Lusztig polynomials, namely, of type -1: $P_{x,w}^{I,-1}$ and of type $q$: $P_{x,w}^{I,q}$. See KAZHDAN–LUSZTIG AND R-POLYNOMIALS, YOUNG’S LATTICE, AND DYCK PARTITIONS
My question: What is the meaning of $-1$ and $q$?