What is NRML Reversal

Client have cover order in nifty with 5025 qtys ,due to yesterday problem in terminal ,at that time he made profit of 1,11,543/- from your side place nrml reversal order placed (sell 5025 qty nifty fut in nrml ) my question is why not sell nifty fut in MIS instead of nrml,- can you explain me