Why was the amount shown on the screen lower than what was printed on my printed federal return? Then the IRS wanted more money that that when they received my electronic return.

Do you have a state refund?  You might have been seeing the net combined federal and state.  At the end Turbo Tax just shows you the net federal and state combined. But that is only for your info. You will still get the full refund and need to pay a tax due. 

Did you pay the amount on the printed 1040?  Then the IRS sent you a bill for more?  How much more?  Could it be for interest or a penalty?

A common adjustment is if you claimed the Recovery rebate credit on 1040 line 30 when you already got the Stimulus payment or got the second one after you filed or reported the wrong amounts or entered them in the wrong box.  Do you have an amount on line 30?