प्रयागराज एक्सप्रेस - जो भी हो तुम खुदा की कसम; लाजवाब हो

when searching trains between two stations,trains are displayed with details which is very useful for us.but under quota,i see tatkal is also mentioned.i wonder how can it fall under tatkal quota.i mean i may not a purchase tatkal quota ticket.please explain this.thanks

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