And that is it! I love using it for when I need to explain how I use whatever new software my company is trying to adopt and it helps me record the process so that I don't need to repeat myself when teaching others how to use the new software. Once done you just click on the extension button again and select the 'stop recording' option and it gets saved automatically to your google drive if you are online and when you are offline it will just save it to your computer.
This is great for tutorials and how-to videos. Once you hit zero you can start speaking and showing others whatever you want. And yes, you are able to choose how long you want the countdown to be. Just download the extension and viola! Whenever you need to record your screen with voice-over just click on the extension, choose your preferences, click record select which tab or screen (if you have multiple screens like I do) and wait for the countdown. I show them step by step on what to do so that there is no room for misunderstandings and everyone is on the same page. I use it mostly to record any procedures or even any task that I want others to get done.