Hi cryptocurrencyb,
The number beside your username is your Reputation score.
It can either go Up or Down.
To make your Reputation go Up,
You must receive a lot of 'upvotes' on your posts and comments.
Therefore, it is wise to post 2x a day,
and make as many comments as possible .
Hope this helps you!
Thanks for the response @phrase. Yes, getting upvotes will increase the reputation but the example of user I have given in my post didn't have that many upvotes too. Still higher reputation! That made me curious.