I've been measuring mine since before Valorant, and I see a lot of people on here feeling demotivated about their human benchmark results so here are a few key points for ya'll:

1. RT is device/test dependent.
2. Keep your finger on the mouse button, with some pressure, every millisecond counts, hovering your finger or keeping it relaxed will inevitably add extra time.
3. Screen brightness matters, the higher the better.
4. Kind of obvious but, reaction time matters on your physical state, make sure to have had proper sleep, be hydrated, exercise, etc etc.
5. Music/Sounds increase reaction time.
6. If you zone out staring at the screen, move your eyes around a little and refocus.
7. There can be some improvement through practice, I think you get your true reaction time only after doing it for a while, once you get there you can't improve anymore.

Ofcourse, needless to say, reaction time alone is not going to make you a god or garbage at the game, its just one of the many factors involved in the game, the other factors having much more room for improvement.