The script will by default look for numbers to replace in elements with the class fs-dynamic-number. In some cases, especially when the phone numbers are already tagged with another class, it's rather handy to tell the script to look for the existing class name. In order to do that, call addElementClass with the class name as a parameter. See example below.

__fs_conf.push(['setAdv',{'id': 'xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx'}]);
__fs_conf.push(['addElementClass', 'my-tagged-phone-numbers']);