How to add backdoor Roth IRA information with contribution for this and previous tax year?

Hi,

For the year 2018, I made two $5500 contributions to my traditional IRA, both before March 2018. First one for 2018 and second one for 2017. I did not make any such contribution for 2017, so there no excess. 

Then I converted over both $5500 amounts to my Roth IRA, essentially doing the backdoor Roth.

So my 1099-R has $11000 as both Gross Distribution and Taxable Amount.

I followed this article

https://ttlc.intuit.com/questions/3582070-backdoor-roth-ira-contribution

But in the end it says I have a penalty of $330, so 6% of $5500. No increase in taxes, so that's good. 

Out of that 11000, I think there has to be a way to tell all of that was not for 2018, but was for 2017 and 2018.

How do I solve this problem?