Although the specific structure is missing from the provided text, the number of $\pi$-bond electrons can be calculated by multiplying the number of $\pi$ bonds by 2 (since each $\pi$ bond consists of a shared pair of 2 electrons). In the original NEET 2015 question, the given structure contained exactly 4 double bonds (which implies 4 $\sigma$ bonds and 4 $\pi$ bonds). Therefore, the total number of $\pi$-bond electrons is $4 \times 2 = 8$.