Hi, if I contributed $6,000 to my Roth IRA in June 2020 can I contribute another $6,000 in January 2021 without it thinking that I exceeded my limit for 2020 tax yr?

I am unsure because you can contribute to your Roth IRA and have it count as a 2020 contribution all the way until April 15th, 2021. Therefore, if I contribute $6,000 in 2020 and another $6,000 before April 15, 2021, will it think I contributed $12,000 for 2020?