What do these games mean 3 | 0 and 15 | 0 ?

I don't understand what they are refering to. Can someone please explain?  Thanks 

* I meant 15 | 10

it means there's 15 minutes on the clock however after every move you gain 10 seconds for example if it took me exactly one second to make my first move the time the me would 15 minutes and 9 seconds. 

Thank you ginger. What about 3 | 0 ?

3 minutes no time added. probably a glitch.

The number on the left side is the amount of time you start with and the number on the left side is called the increment and it is the amount of time that you get with every move. For example if I was playing 15l10 rapid and I took ten seconds to make my first move the clock would say I had 15 minutes remaining. The math behind this is 15-10+10=15. 

Yeah I think it was a glitch b/c it now shows 3 | 2.  Thanks all