Treating the $10,000 as a CRD simply allows you to get the money back into the SEP-IRA as if you never took that money out, but does require you to include Form 8915-E with your 2020 tax return to report the CRD and its repayment before the due date of your 2020 tax return.
Entirely separately, you treat $10,000 of the original $30,000 deposit as your a SEP contribution for 2020 and report it as such on your 2020 tax return. The result is that you will have reported a SEP contribution of $20,000 on your 2019 tax return and a $10,000 SEP contribution on your 2020 tax return, treating your $30,000 deposit as being simultaneous contributions of $20,000 for 2019 and $10,000 for 2020.
