enum stores data remains stored in the static variable of an enumeration even if the view controller dismisses

I have a problem and do not know what to do. My FirstViewController calls with

let secondVC = SecondViewController()
let navController = UINavigationController(rootViewController: secondVC)
navController.modalPresentationStyle = .automatic
self.present(navController, animated: true)

my SecondViewController. In the SecondViewController, user can make various selections, such as selecting numbers. The selected numbers are stored in a static variable of an enum located in the SecondViewController. (Why I do it this way is not important right now).

enum Numbers {
     static var selectedNumbers: [Int] = []
}

If I return to my FirstViewController with dismiss the SecondViewController and then go back to my SecondViewController, I see that the enum from the SecondViewController still has the user's selection stored. What exactly is the reason for this? And can I somehow prevent or solve this?

According to your expectation, I recommend changing the static to store property in SecondViewController, and a callback to handle if needed, something like:

class SecondViewController: UIViewController {
    ...
    private var selectedNumbers: [Int] = []
    var onSelectedNumbers: (([Int]) -> Void)?
}

In FirstViewController, when you pop back from SecondViewController, handle selected here:

let secondVC = SecondViewController()
secondVC.onSelectedNumbers = { [weak self] numbers in
    //TODO:
}
let navController = UINavigationController(rootViewController: secondVC)
navController.modalPresentationStyle = .automatic
self.present(navController, animated: true)

And if you still want to use static one, you can clear static property whenever SecondViewController is dismissed:

class SecondViewController: UIViewController {
    ...
    func dismissViewController() {
        //TODO: call this function manually
        self.dismiss(animated: true) {
            Numbers.selectedNumbers = []
        }
    }
}