My textbook says “Among K⁺, Na⁺ and Cl^-, K⁺ contributes to the resting membrane potential the most, because it has the greatest permeability across the membrane.”

I agree with this, but I’m just curious: why is the equilibrium potential of Cl^- (-75mV) closer to the resting membrane potential (-70mV) than that of K⁺ (-90mV)?