What do we count in the $e^{+}{e}^{-}\to Z$ neutrino counting experiment?

We find that the difference between $N_{\nu }=\frac{{\Gamma }_{\mathrm{inv}}}{{\Gamma }_{\overline{\nu }\nu }^{\mathrm{SM}}}$ and ${\overline{N}}_{\nu }=\frac{{\Gamma }_{\mathrm{inv}}}{{\Gamma }_{\overline{l}l}}\frac{{\Gamma }_{\overline{l}l}^{\mathrm{SM}}}{{\Gamma }_{\overline{\nu }\nu }^{\mathrm{SM}}}$ 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 $N_{\nu }$ and ${\overline{N}}_{\nu }$ could be a test for the bidoublet contents, assuming that nonstandard radiative corrections are negligible.