A subscriber can be in multiple tags at the same time. If, for example, you want to see all subscribers that are only in the BackInStock tag and not in the CartInProgress tag, you can exclude these subscribers in a segment. To do this, you create a segment as usual. And then you choose tags that the segment should be based on, in this case BackInStock, then you choose the tag you want to exclude. To do this, you write "-" (minus) before and choose the tag.

The result of this segment will then show only subscribers that are only in the BackInStock tag and not in the CartInProgress tag.