A death is counted every 8 seconds.
You can't alt-tab the game for doing something else because it pauses.
Do this when you have other things to do, like study something or watch a movie.

Select Extras, then Stats to see your total deaths:







(these are my statistics)

Get this achievement as last thing in the game.

https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2942167132
Check out this other guide I made:
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=3122208693
Take a look at my YouTube channels:

Main YouTube channel

Gaming YouTube channel



Have a good day!