Having an accurate count of your newsletter subscribers is vital to tracking the effectiveness of your marketing efforts. Opted out subscribers won’t receive your newsletters or other mailings, but will show up in subscriber counts. One way to correct this is to automatically unsubscribe them from your list when they opt out of all email marketing.
To do this, go to Marketing→Settings, then click on Email Defaults. Go down to the Email section, and click Actions next to When Someone Opts Out of All Email Marketing. This will allow to do a number of actions when someone opts out of your Infusionsoft email marketing, such as removing or adding a tag, changing the value of a field, or creating a task.
If you use custom fields to track your subscriptions, then you can change the value of the field to unsubscribe them. If you use tags, you can remove the tag. This will remove the contact from subscriber counts so you can easily know the true size of your list.