Indusind has tiered rewards system. And the tiers change at 5k,10k,20k and 40k. If bill payments are done as entire slabs (5/10k/20k/40k), they calculate currently. But if we do other amounts like 7320, for example, they calculate correctly for the first bill, but they mostly don't calculate correctly after that, it becomes unpredictable.
If you go through this thread, there'll many complaining about that. I was also confused in the beginning, but later found that if we do in rounded numbers as in their tiers , 99% of the time, they calculate correctly