Poisson-like statistical fluctuations, which are caused by the finite number of produced particles, are estimated for the cumulants of conserved charges, i.e., net baryon, net electric, and net strangeness. They turn out to be the same as those baselines derived from the hadron resonance gas model. The energy and centrality dependence of net-proton cumulants at the Relativistic Heavy-Ion Collider (RHIC) are demonstrated to be mainly caused by statistical fluctuations. By subtracting the statistical fluctuations, the dynamical kurtosis of net- and total-proton cumulants from two versions of a m...