from typing import List


def calculate_depth_increases(contents: List[str]) -> int:
    """Calculate the number of depth increases.

    Args:
        contents (List[str]): the file contents

    Returns:
        int: number of increases in depth

    """
    increases = 0
    prev = int(contents[0])
    for line in contents[1:]:
        depth = int(line)
        if depth > prev:
            increases += 1
        prev = depth

    return increases