Number of antibonding electrons in ${\mathrm{N}}_2$ is :

$N_2\to 7\left(2\right)=14e^{-}$

$N_2\left(14\right):\sigma 1s^2\sigma *1s^2\sigma 2s^2\sigma *2s^2\pi 2p_x^2\pi 2p_y^2\sigma 2p_z^2$

$e^{-}\left(BMO\right)=10$

$e^{-}\left(ABMO\right)=4$

Number of antibonding electrons in ${\mathrm{N}}_2$ is 4.