Usually equal to 3-4 seconds when the computer is new.. After one month of use though, this turns into 10-15... and After a year you might as well go to bed if it tells you it has one second left.
"One second left on download" ..... 20 minutes later......
"One second left on download" ..... 1 microsoft second later.... you wake up from your 3 hour nap
A screen during any installation in Windows showing "1 second remaining" that lasts a few minutes.
"I don't have time to talk to you, I'm almost done installing the game - it says I only have one second remaining."
"Dude, you have plenty of time, it's a Microsoft second."