Why did my market order in the pre-open session become a limit order?

Pre open market is defined as the time of trading that takes place before the regular market time (i.e on buy or sell the stocks before the market time starts).

Every day, the pre open trading session normally lasts from 9 am to 9:15 a.m. IST. So any unmatched market orders in the pre session will transfer to the regular market as a limit order to maintain the original time stamp. These orders are executed at the equilibrium price. In case if the opening price of the market order did not define than the market order carried over the previous day of closing price.