```typescript
export function stepValue(step: string): number {
  if (step === "+") return 1;
  if (step === "-") return -1;
  return 0;
}

/** The running total after each instruction. */
export async function scanTally(steps: string[]): Promise<number> {
  let total = 0;
  for (const step of steps) {
    total += stepValue(step);
  }
  return total;
}
```