what does 15/10 mean

You get 15 minutes at the start, and then 10 seconds are added to your clock after each move. 

Here's another thread regarding the same question~

https://www.chess.com/forum/view/help-support/what-does-15-10-mean

thanks everyone l understand now

What does the screen show?  Does a player’s time show on the screen?

This is a 15-minute game with 10-second increment, meaning that both players start with 15 minutes on the clock, and 10 seconds are added onto that player's clock for every move they play.

For the fun of it, honestly, I decided to revive a thread from 2009.

Yep, you'll see the time there at the same spot just as it normally is in regular games without increments. 

That is what I now play because too many people take too long in 30 min rapid, but what does 15 10 typically work out to?