I contributed $6000 to my traditional IRA account for the tax year 2021 in Feb'21.

Later in the year, I switched jobs, and at my new employer, I started a 401k plan. As I'm participating in an employer-sponsored retirement plan, I cannot deduct the contribution to IRA anymore from the taxable income for the year. Therefore, I want to reverse the $6000 contribution.

My understanding is that I can withdraw the same year contribution before the tax filing deadline i.e April 15, 2202. Along with the original contribution ($6000), any interest/earnings generated has to be withdrawn as well. And I have to show ONLY the interest/earnings as part of gross income while filing taxes and also pay a 10% penalty ONLY on the interest/earning generated and NOT on my original contribution ($6000). 

I want to confirm if my understanding is correct so that I can go ahead and perform the distribution. Thank you.

Reference: https://www.irs.gov/instructions/i5329#idm139986644641968 "Line 15"