Based on last two year's record, USCIS will definitely get more than allocated limit within first few days of April. USCIS typically gives first five business days (April 1 - 7 this year) to wait before they announce the cap has reached. So if that's the case, an application reaching USCIS on April 1 or April 7 will have same probability of getting selected. As hawachawa state, application reaching USCIS after April 7 will not enter the lottery and gets returned back.