  We evaluate the eigenvalues of Dirac operator in the background of
instanton-anti-instanton configuration (I-$\bar{{\rm I}}$), in a simple
(1+0)-dimensional model, and find that quasi-zero-mode disappears for the
closely localized I-$\bar{{\rm I}}$ configurations. This result suggests that
the configurations which are dominant at high energy in the valley method are
actually non-anomalous ones and irrelevant to fermion number violation. Hence,
there seems to be no theoretical basis for expecting anomalous cross section to
become observable at energies of 10 Tev region in Weinberg-Salam theory.
