I have 2023 and 2024 IRA contributions on single 2024 1099-R ($13,500), but getting excess contribution error. How do I do backdoor Roth when both years are on the form?

After filing my 2023 taxes, I contributed to a 2023 backdoor Roth prior to April 15, 2024. Later in 2024 I contributed towards my 2024 backdoor Roth. Now, I have a 1099-R with two years of contributions on it, totaling $13,500. How do I report this backdoor Roth without getting the excess contribution error?