How can I make the list decimal numbers bold?

How can I make the list decimal numbers bold?

1. first item
2. second item
3. third item

I found a solution here: http://stackoverflow.com/questions/21369843/is-there-any-way-to-make-numbers-in-ordered-list-bold and works like a charm on standard html but when I add that code to my Sahifa Custom CSS I get a strange result like this one below:

  1. 1. first item
  2. 1. second item
  3. 1. third item

Can anyone explain what’s going on?

Thank you!