Before revision:  The present metricis able to quantify the numerical overshoots of shock-capturing schemes , and some new features of several canonical schemes are shown .
After revision:  The present metricis able to quantify the numerical overshoots of shock-capturing schemes are analyzed accordingly, and several findings including the amplitude of overshoots non-monotonously varying with the CFL number, and the amplitude of overshoots significantly depending on the reduced wavenumber of the square waves (discontinuities), are newly discovered, which are not before .