  We present an analysis of the Counts-in-Cells (CiC) statistics of subhaloes
in the publicly available IllustrisTNG cosmological simulations (TNG100-1,
TNG100-3 and TNG300-3), considering their full and dark-only versions, in
redshifts ranging from $z = 0$ to $z=5$, and different cell sizes. We evaluated
two CiC models: the gravitational quasi-equilibrium distribution (GQED) and the
negative binomial distribution (NBD), both presenting good fits, with small
detectable differences in the presence of baryons. Scaling and time
dependencies of the best-fit parameters showed similar trends compared with the
literature. We derived a matter density-in-cells probability distribution
function (PDF), associated with the GQED, which was compared to the PDF given
in Uhlemann et al. (2016), for the IllustrisTNG 100-3-Dark run at $z=0$. Our
results indicate that the simplest gravithermodynamical assumptions of the GQED
model hold in the presence of baryonic dissipation. Interestingly, the smoothed
(density-in-cells) version of the GQED is also adequate for describing the dark
matter one-point statistics of subhaloes and converges, to subpercentage levels
(for an interval of parameters), to the Uhlemann et al. PDF in the high density
range.
