  I investigate the volume corrections on cumulants of total charge
distributions and net proton distributions. The required volume information is
generated by an optical Glauber model. I find that the corrected statistical
expectations of multiplicity distributions mimic the negative binomial
distributions at non-central collisions, and they tend to approach the Poisson
ones at most-central collisions due to the "boundary effects," which suppress
the volume corrections. However, net proton distributions and reference
multiplicity distributions are sensitive to the external volume fluctuations at
most-central collisions, which imply that one has to consider the details of
volume distributions in event-by-event multiplicity fluctuation studies.
