2018 backdoor roth question

I was doing some research on how the 3.8% tax on investment income would impact me. it got me to looking at my 2018 taxes. I see something I don't understand in regards to my backdoor roth. I can't download the software. Trying to see if i made a mistake on my backdoor roth. Can anyone help?

On my 1040A:

Line 4a: Shows 5,500

Line 4b: Shows 0

 

Line 6 however, shows a value that includes line 4a. So, it appears my IRA got input in as taxable income.

 

My form 8606 15c shows taxable amount of 0, as does line 18

 

Did i pay taxes i shouldn't have?