```python
def swap_case(text: str) -> str:
    """Text with the case of every letter turned over."""
    return ''.join(char.lower() if char.isupper() else char.upper() for char in text)
```

Explanation:
- The function `swap_case` now iterates through each character in the input string `text`.
- For each character, it checks if it is uppercase using `char.isupper()`.
- If it is uppercase, it converts it to lowercase using `char.lower()` and appends it to the result.
- If it is not uppercase (i.e., it is lowercase or a digit), it leaves it unchanged and appends it to the result.
- Finally, it joins all the characters in the result list into a single string and returns it.