You were right. It was 4 devices after all. I guess the number of devices mentioned on Paytm was incorrect (except the first page).
The price was only Rs.999 on Paytm (may be they are running some kind of offer?). They also have Zee5 Subscription Gift Cards, but the 4K Plan in that still costs Rs.1499 (along with a 10% Paytm cashback, which is Rs.150). The 999 one is a direct Zee5 Subscription purchase from Paytm. Like I had mentioned in my earlier comment, they are activating it for whichever mobile number we provide during the purchase.
I also received Rs.50 as Paytm cashback (by applying the code ZEE50).
Plus I had not opened Paytm for a very long time. So I'm not sure if it was because of that, but I also received Rs.70 cashback for adding money to the Paytm wallet (I always add money separately & do the payments separately).
So 999 - (70 + 50) = 999 - 120 = 879.
Final Cost = Rs.879.
I guess that's a good deal.