Greetings!
Welcome to Microsoft Q&A forum.
I understand you are looking to troubleshoot an issue that occurred on June 18th. If your backup retention period is set to the default of 7 days, this would align with the earliest available restore date of June 20th, as observed in the portal. Therefore, you cannot see an earlier Point-in-Time Restore (PITR) date.
Regrettably, due to the current backup retention policies, restoring to a date earlier than June 20th is not feasible.
For a detailed overview of backup settings and policies, please refer to the following documentation: Automatic, geo-redundant backups - Azure SQL Database | Microsoft Learn
Thank You!