Any way to evade IDFC CC reward redemption fees of 99+gst ?

I get 1 option, a checkbox specifically, during card payment which asks me if i wana redeem my points towards this payment. Has anyone used that ? How does that work? Are we charged lesser outright or do we pay the full amount and reward points show as credit in statement later? are you still charged 99+gst for this method?

the other option is to go on their reward points website and pay the 99+gst fees to get a giftcard