Today would shed some light on the cmdlet “Enable-ADSyncExportDeletionThreshold” which comes with the Azure AD Connect. If you are using Azure AD Connect to synchronize your On-Premise Active Directory to Azure Active Directory, Azure AD Connect will never execute a batch of more than 500 objects to delete. You can check the current value by using “Get-ADSyncExportDeletionThreshold”:
So this means, you should consider to adjust this value to your needs. If a misconfiguration is happening, and a huge amount of objects is no longer synced to Azure AD, this may interrupt some business. And what means huge for your business? If your business consists about 5000 users, allowing to delete 499 Object a once could be too much.
See also this Microsoft Article: Azure AD Connect sync: Prevent accidental deletes