When setting up your retargeting campaign, converters will be excluded automatically.

It's false that converters are automatically excluded from retargeting campaigns. While it's best practice to exclude users who have already converted (e.g., made a purchase, filled out a lead form) to avoid wasting ad spend and annoying customers, this is a manual setting you must configure within your ad platform. You typically achieve this by creating an audience segment of converters and then excluding that segment from your retargeting campaigns. If you don't manually exclude them, they will continue to see your retargeting ads.