In the discussion, there is clarification on the term "[HA]" in the equation Ka = [H+][A-]/[HA], which refers to the equilibrium concentration of the acid rather than its initial concentration. The initial concentration, sometimes called formal or analytical, is represented as [HA] + [A-]. A key point raised is the necessity of including both [H+] and [A-] in the numerator of the Ka expression. It is explained that using only one of these concentrations would be insufficient, as both are products of the dissociation reaction. Changes in the concentration of either [H+] or [A-] affect the equilibrium, thus necessitating their presence in the equation to accurately represent the acid dissociation constant.