The curves of differential capacitance of the electrical double layer dense part in the Hg/(H2O + NaF + n-C4H9OH) are calculated by using the equations of the model of three parallel capacitors, with the corresponding adsorption parameters fitted. The curves of full differential capacitance in the system are calculated, basing on the obtained results combined with the classical theory of the diffuse layer, for the following concentrations of the supporting electrolyte: 0.003, 0.01, 0.03, 0.1, 0.3, and 1 M. By using the curves’ regression analysis it is shown that they agree very well with the model of two parallel capacitors, when six effective adsorption parameters are appropriately selected (provided the linear potential dependence of the effective attraction constant is allowed for). The dependences of all model’s effective parameters on the NaF concentration are found; they correspond well to the analogous experimental dependence in the system under study.