I'm not an expert on form 8615.
It appears that for line 10, you used the parents actual tax. In TT, you are not asked for the line 10 amount. TT calculates it for you. It's $15,497 when line 9 is 18,765.
You may need to follow the instructions for line 9. https://www.irs.gov/pub/irs-pdf/i8615.pdf
To "play around" with TT, you need to use the download program. You can't do trial stuff in the online version.
