Get the number of cells from the z score

[Ping-lin14]

Hello.
I would like to know if there is a way to calculate the number of cells through the z score.
For example, I want to know how many cells have z:NFKB1 greater than 1.

[rcorces]

getAvailableMatrices(projHeme5)
motifMat <- getMatrixFromProject(ArchRProj = projHeme5, useMatrix = "MotifMatrix")
zMat <- assays(motifMat)$z
length(which(zMat["RORB_865",] > 1))