Borlabs Cookie stores the JavaScripts that set the cookies, such as Google Analytics.
Since Borlabs Cookie does not execute this JavaScript until the visitor has given their consent, this cookie is not set until then.
With an opt-out, the JavaScript is no longer executed, which means that a cookie is no longer useful. However, no cookie will be deleted. The effects of an opt-out are only noticeable after the website has been reloaded, then the JavaScript is no longer executed.
To stick with the Google Analytics example, after an opt-out and after the website has been reloaded, Google Analytics would no longer run.
If you want to run Google Analytics using Borlabs Cookie, you must remove any JavaScript executing Google Analytics outside of Borlabs Cookie.
Often the JavaScript is stored in a special field in the theme settings. This code must be removed.
If the JavaScript is loaded by a plugin, e.g. MonsterInsights, the Script Blocker of Borlabs Cookie must be configured for this.
In other cases, the cookie may come from the integration of external content, e.g. a YouTube video or a partner badge, which are integrated with the help of an iframe. This content must be blocked using the Content Blocker. If this does not work automatically, the shortcodes of the Content Blocker must be used.
So if a cookie is already set on the website before you give your consent, you need to find out where the cookie came from. You can find an article that can help you with this here:
Once you have found the location, you need to check if you can simply remove the code and integrate it via a Cookie in Borlabs Cookie, or if you need to use the Script Blocker or Content Blocker.