Why do I have both box 2a (1099-DIV) and at the same time capital gains from form 8949 entered into my Schedule D even though they are from the same broker?

Capital gain distributions entered from your form 1099-DIV are transferred by TurboTax to line 13 of Schedule D. Form 8949 only summarizes capital gains/losses entered from forms 1099-B and the totals are then transferred to Schedule D lines 1 to 3 and 8 to 10. There is no double counting of the capital gains distributions from form 1099-DIV.

Edited 04/04/2019  |  7:28 PM PST

Yes logically it should be that way, but what I see is this: Box 2b (1099-DIV) got entered as box 13 on the schedule D and my 8949 got entered in box 8b on the schedule D and then added together.

Please see my edited answer.