```python
def step_value(step: str) -> int:
    if step == "+":
        return 1
    if step == "-":
        return -1
    return 0

def scan_tally(steps: list) -> list:
    """The running total after each instruction."""
    total = 0
    running_totals = []
    for step in steps:
        total += step_value(step)
        running_totals.append(total)
    return running_totals
```