Your numbers are correct.
You can treat the almost $200 as part of your 2020 SEP contribution because it's your responsibility to allocate the contributions made between January 1 and the due date of the previous year's tax return to a particular year. Just make sure that your personal tax records identify that the almost $200 that was contributed in July 2020 was for 2020 and that only the other roughly $18,000 was for 2019.
