Once you have generated a Tag, it will not change. For example, if you create a rule and then decide to change the images in the rule, upon saving the changes, the Tag will remain the same. All changes will automatically pull through. You only need to add the Tag to the HTML once.
To edit a Tag, navigate to the Tag you wish to edit. Click on the 'Edit Tag' button:
Proceed through the steps, making the changes as required. The Tag generated after this process will be the same as the original Tag. Therefore, if you've already added the Tag to the HTML, you won't need to change it. All changes will automatically pull through to the Tag.