Create Minecraft Speedrun Timer?

I want to try to start a speedrun in Minecraft and all speedrun Youtubers use a timer like that. How can I have the timer? What do I have to install there?

Here is a link from what I mean:

Left the timer.

The software is called LiveSplit (https://livesplit.org/). Whether it is worthwhile for private runs, of course, is another question, because then you can just 'nen timer on the phone or something.