The bug is that the condition is inverted: `score < floor` should be `score >= floor`. The current code marks entries below the floor, but the docstring says "reach a floor" (i.e., equal or above).

```python
def mark_list(scores: list, floor: int) -> list:
    """Scores written out, with a star against those that reach a floor."""
    out = []
    for score in scores:
        out.append(str(score) + "*" if score >= floor else str(score))
    return out
```