Hi paulr44860813,
It makes sense that the visit count is higher when you look break it down by tracking codes. A visit can easily have more than one tracking code. Example:
the user goes to google, searches for product A, find your paid advertisement and click through to your website, the tracking trigger campaign A in AA and registers 1 visit. The user is not interested in the product and goes back to the google search result page and searches again, not another paid ad shows up which has campaign B tracking code. If the user clicks through on this paid ad as well, then you will also have 1 visit registered to that campaign.
In your first data extract (without the campaign tracking code), you will just see 1 visit, because the user had 1 visit within the 30 minute window. When you break it down with campaign code, you will see more visits as there is 1 registered for each campaign code.
Hope the above makes sense.