When I fill out a Schedule A long hand, my deductions total $20,005. TurboTax is using the std deduction $15,100. This will cost me approx. $1000 more in tax expense.

There are two things you can check.

The first one is to go through all of your input to make sure it was done correctly.  You may have a number in the computer that doesn't match your added up deductions.

The second one is to go through the return.  Click Done with Deductions after you've double-checked the amounts.  Depending on what your return looks like, you'll see a screen that has three colored progress bars and says Analyzing your Return.

Continue till you get to a screen that says Let's See if the Standard Deduction is Right for You. There's a check box at the bottom, Change my deduction.  Check that box, and see if anything changes.

If you still need more help, post back to THIS thread.