Information Management Policy - SharePoint list - Retention not applied for existing items in a list

I have a SharePoint online site which has a list where we have enabled 'Retention' under Information Management Policy settings. The policy has to delete items from the list that are older than 6 months (Created date). However, despite configuring correctly the policy seems to not have applied as none of our older items got deleted. The list has around 8500+ records and the policy was created very recently. Can anyone suggest what might be the reason ? Below is the snapshot of the configuration: