Each of your contacts has an 'Opt-in type' contact data field, which contains the opt-in type of that contact.
Segmenting contacts who have a verified double opt-in type
- Go to Contacts > Segments
- Click on New segment and enter a name for the segment
- Drag and drop the 'Data fields' rule into the drop area titled 'Include contacts that match all the rules in this group'
- Click the rule and select Opt-in type from the contact data fields list
- From the dropdown that next appears, select Verified double
- Click OK
- Click Save
- Click Generate count
The number of contacts in the segment is displayed.
Find out more about segmentation