Mate, I think this is what happened:
Your cashback amount was 1275.
Let’s assume your total bill amount was ₹22345 (before considering the cashback).
You paid the full ₹22345 to your credit card (before the cashback could adjust). In reality, you were only supposed to pay ₹21070 after adjusting for the cashback.
This means you overpaid by ₹1275 because you didn’t account for the cashback on your statement. That’s why they refunded the excess amount to you.
Post your statement here, you can hide your transactions.