10 seconds are added to your time after each move.
15/10 live chess

You get 15 minutes for the game, plus 10 additional seconds on your clock every time you make a move.
For x|y: you get x min. and y additional seconds.
You get 15 minutes for the game, plus 10 additional seconds on your clock every time you make a move.
For x|y: you get x min. and y additional seconds.
What does the second number (in this case the 10) refer to when I play live chess?