```python
def seat_block(label: str) -> list:
    if not label or not label.isalnum() or len(label) != 3 or label[1] not in 'ABCDEFGHIJKLMNOPQRSTUVWXYZ':
        raise ValueError("Invalid seat label")
    
    row = int(label[:-1])
    letter = label[-1].upper()
    
    return [row, letter]
```