They reply to the RTI Request within a week, in which they'll ask to send a Demand Draft by Post to Kolkata, of around 650 Rs. for both group or 400 Rs. for Single Group. Ofc, with it, you shall mention ur RTI Request no. etc. Normally it'll be around 20 days, till the letter reaches the right person in Kolkata. Then expect another 1 month for the reply. You may get the scanned copy by email most probably, or B&W photocopies by Post. Basically, applying today, expect it to take a minimum of 1 month if you're lucky, And 2 months, if a bit short on luck.