When the Intruder portal launches your monthly assessment (or your create a retest from the dashboard), it sends a list of your targets to our scanning engines and once the scans have started the targets included in those scans can no longer be updated.
Hence any target changes (i.e. adding or removing targets) will not be effective until the following assessment.
On the targets page in the portal, it will flag any targets that were not included in the latest assessment with a yellow exclamation mark:
Any new targets will obviously be included in your next monthly assessment.
If you're on a Pro or Verified plan, you can also create a retest at any time to test all your targets for weaknesses immediately.