After struggling with this same problem for hours, I found this post. If you follow DanaB27 instructions you will get the right results: your after tax contribution to T-IRA (6000 or 7000) won't impact what your federal tax due.
Now it's ridiculous that Turbotax hides this step to the point where we need to keep searching for answers, find an expert who provided the proper steps, which involves a manual search on the help bar to find the entry point. I wonder how many people over paid their taxes due to this issue.
