Were you under 21 when the IR2 petition was filed?
if yes you don’t have to worry because Your age would have been frozen as at the day the petition was filed , IR2 can’t age out, the only thing that can change your category is if you get married.
i think it’s a glitch from their end, most ir2 that are above 21 as at the time they receive interview letter have this issue….. but most times it changes back few days before the interview