In my particular case,  my client had a total income of $56k yet the full ($1,800) amount was deducted.  ( Ie. Client had a tentative refund of $1,500.  After I entered the $1,800 stimulus checks now shows she owes the IRS $300.   What am I doing wrong????

So your client is entitled to the full 1800, but they already got it advanced to them during 2020, so they don't get it on the tax return.

If they had not gotten the advances, then they would see it credited on the tax return.