Schedule A line 17 & Form 1040 line 12a inconsistent

I used TurboTax Premier to prepare my 2021 tax.

 

The line 17 of Schedule A is 13,503. The line 17 says this figure is to be filled in Form 1040 line 12a. However, when I checked the line 12a, it was a different figure, 21,323. Why are these two figures different?