Using a phenomenological grinding kinetic theory based on the pace of the process as described by the selection function (S_i) and breakage distribution function (B_i,j), the estimated grinding performance of a mill can be approximated. This method is now widely accepted and has been thoroughly explored by renowned scholars such as L.G. Austin. Despite wide acceptance of this method, insufficient studies were conducted on the kinetic model for fine sieve sizes. Since there is no extensive investigation on the fluctuation of model parameters over various sieve size groups, this paper presents one. Simulation models for the design of ball mills are included in the software for the digital layout of mineral processing circuits. The MODSIM© simulator calculates nearly complete mass balances for each mineral processing plant and simulates integrated flow diagrams including grinding. The S_i and B_i,j equations were derived using the particle size distributions at varied grinding times and with model parameters for coarse and fine particle size groups. Experimentally derived data were statistically compared to the MODSIM© simulator data using model parameters.