Retirement tax questions

1.  On my Form 1040-SR, Box 4a is empty but Box 4b has the taxable amount of my IRA distributions. Shouldn’t there be an amount in Box 4a?

 

2.  Also, on Page 2 of my 1040-SR, there is an amount in Box 12a and the same amount in Box 12b but there is no Schedule 2 or any other worksheet to explain where TurboTax came up with the amount in 12a/12b. [See next question.]

3.  On Page 2 of Schedule D, Line 16 has an amount. Line 17 is marked “Yes”. Lines 18 and 19 are blank. Line 20 is marked “Yes”. It says to complete Qualified Dividends and Capital Gain Tax Worksheet in the instructions for Form 1040-SR, Line 12a. I printed out my whole return but I do not find this worksheet. Does it have an Attachment Sequence No.? Obviously my questions 1 and 2 are related because they both deal with Line 12a but I’m afraid to send in my return if there is a Worksheet or Schedule 2 missing. 

Thank you so much for your help. My husband always did our taxes on TurboTax software but he passed away in February so it’s my first time.