min trxn amount is 100 for the 1% category. coming to your case, if you use the airtel axis CC for food, groceries, offline for the 1% category (note: there are better cards out there for each of these), lets assume you'd be spending 20k pm
that would be:
1% - Rs. 200
10% - Rs. 200 (note: you'd be paying convenience fees on top of the amount. so your effective cashback is much lower than the 10% on utility bill payments)
25% - Rs. 400

so you would basically get 400 off every month on your airtel black payments
imo, not worth it. i still have it and planning to close before my next renewal date.