Each scan must be for campgrounds within the same geographic area for which you're searching. For example, if you want to take a trip to Boise, ID all the campgrounds available to select in a single scan will be scan-eligible campgrounds in the similar area. You are only offered campgrounds, as choices for the scan, that fall in a similar area to the original search choice.

If you want to choose a scan-eligible campground as an alternate option and it's not offered in your choices, then it falls in a different geographic area and will require another paid scan for alerts.