Using TT Download for Windows for 2021. I enter amount for 1099-NEC. But the Summary in TT or the 1040 forms mode, show different lower. amt. Why?

Exactly where does it show a lower amount?  The gross 1099NEC amount should be on Schedule C line 1.  Then the Net Profit or loss from Schedule C line 31 shows up on Schedule 1 line 3 which goes to 1040 line 8.  Switch to Forms mode and open Schedule C to check your entries.