The way we implemented the timer is not particularly accurate for time tracking. Let's review the code:
this.timer = setInterval(() => { this.remainingTime -= 1 if (this.remainingTime === 0) { clearInterval(this.timer) }}, 1000)
This means that we decrease the remaining time every second. The problem is that the setInterval function itself is not 100% accurate and may fire the function a bit before or after 1000 milliseconds, depending on the machine's computational load; this way, the margin of error can accumulate and become a considerable amount. A better approach would be to check the clock every time the function gets called and adjust for the error at each loop, though we won't cover that here.
