What do we count in the e+e-→Z neutrino counting experiment?

We find that the difference between Nν=Γinv/ΓbarννSM and bar Nν=Γinv/ΓbarllΓbarllSM /ΓbarννSM can be used as an indicator of possible extensions of the standard model. This test will be possible, however, only after the top-quark mass measurement. We illustrate our point by an example of a left-right symmetric model with the Higgs sector containing one bidoublet and two triplets and the additional assumption that there is no fine-tuning in neutrino Yukawa couplings. If this is the case, the difference between Nν and bar Nν could be a test for the bidoublet contents, assuming that nonstandard radiative corrections are negligible