रेलफैनों की तो बात ही कुछ और है

friends i have booked a berth in 12721 dakshin exp on 23 oct from secunderabad to nizammuddin in sleeper class current status rac 58 i have opted for vikalp option now in irctc there is remark saying ALT train defined you are likely to get CNF accommodation in ALT train.So exactly what does it mean,also i am worried that if i dont get a berth then it will be a great problem for me.

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