The mystery is in the physical value. Not only is the result peculiar, in that three ostensibly arbitrary numbers give a simple fraction, but also in that in the case of electron, muon, and tau, Q is exactly halfway between the two extremes of all possible combinations: ⁠ 1 / 3 ⁠ (if the three masses were equal) and 1 (if one mass dwarfs the other two). Q is a dimensionless quantity, so the relation holds regardless of which unit is used to express the magnitudes of the masses.