What's an countdown timer? 

A countdown timer can be described as an GIF image that countdowns to a specific date and time. These are fantastic for increasing conversions as well as creating the feeling of urgency.

Countdown timers count down until a time/date that you have established. If a subscriber opens the email it will play on loop for about 90 seconds. If you keep it running for too long it will repeat itself each 90 seconds. There's no need to be concerned because the timer will be counting down when you refresh your page. https://timer.live/11-minute-timer