I'm new and I was wondering: How can you precisely count the milliseconds in a run?

Use a timer that counts with milliseconds, could always ask mods for a re-time maybe? I know a lot of editing software have timers you can use also

I myself just use livesplit and with mobile I just use a speedrun timer

Yeah sorry, I realized now that I wasn't clear with my question: I use Livesplit as a timer on PC, but how can you count three digits milliseconds, since when I use it it only has 2? Is there a setting for that or should I use another tool, such as a software post-recording?

Maybe use a different timer as there is no setting to go beyond hundredths, timing up to hundredths millisecond is really all you need though but if you want it to be more accurate, probably just use another timer or try applying maths/math to it (which I don't recommend)

Ok, thank you for your time

We use Slushpuppy retime, it's a software that help us retime runs by using your youtube video : More infos here https://github.com/Slush0Puppy/retime