We present a method for estimating the number of counts as a function of time of a counter with sub-units for which the expected count densities are the same. This is typically given in arrays of photo-multipliers in neutrino experiments, as well as in the segments of one segmented counter for indirect detection of cosmic rays. We take the latter as study case, and simulate and compare the performance of our algorithm in a detector like the Underground Muon Detector of the Pierre Auger Observatory. By properly accounting for the dead time of the counter, we provide estimates of the counts as a function of time to a single time-bin resolution.