the logic is that whenever a train starts from somewhat small station and goes via bigger station to a much longer distance then greater quota is to be provided to bigger station. hardly any passenger wl book from cbe to sbc. if u notice almost half of the train would have come empty from cbe to sbc cos sbc quota has to come vacant due to no booking for that leg.
ps - I hv travelled just once in this train. this is from my experience of ir and not necessarily this train