quantum field theory - Baryogenesis via Leptogenesis

Baryon number is directly violated through electroweak anomaly and so does the Lepton number, for each transition from one vacuum to another. The two violations are of equal amount $\Delta B=\Delta L=N_f[N_{CS}(t_i)-N_{CS}(t_f)]$ since $(B-L)$ is anomaly free. Both the violations (i.e., $\Delta B,\Delta L$) will occur simultaneously for each transition. But in this manner $B$ is violated directly and I do not think that $L$ violation is inducing $B$ violation. Is this true? When standard model is extended with right-handed neutrinos, then decays of heavy Majorana neutrinos give rise additional to $L-$violation. How can this leptogenesis induce baryogenesis?

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