How can I see a detailed calculation for line 16 on form 1040. When I compare the Turbo Tax amount in line 16, it differs to mine.

To see the detail of your Form 1040 Line 16, print out Schedule D Tax Worksheet. 

you can't use the tax table when you have qualified dividends and or long-term capital gains. they get taxed at a special rate.  there are also other situations where you can't use the tax tables.