Good afternoon akeane,
You said you saw two ~ symbols in backgammon game?
I have never seen it, personally I am not very familiar with this game.
Now if it is only one ~ a in the name, it means that:

Provisional ratings  ~ 
Players who have played less than 20 matches are considered to have "provisional" rating. This is indicated by a  ~ sign next to their names.
As per information available at: 

https://www.flyordie.com/games/help/rating_system.html

Best Regards
Dav7d

~.~