it is for lvls. I'm not sure why they do it but the reason I do it is I am normally bursting and my characters lvl. I don't want to come on wlodb every day and say 'ok today my character is lvl 20' then come on the next day and say 'now I have to change my signature because my character is lvl 26' so on my sig I put water mage lvl 2X saying that my character is somehwere between lvl 20 - 29. Not sure why other people do that but that's why I do it XD