victor zsasz’s mark on the head

idk if this is a stupid question but we all know that he has only four marks on his forehead, does that mean that he hasn’t had a chance to fill that untill the arkham knight when he kill three people and posed them as if they were fishing or is that saved up for batman. because i remember him saying that he has a patch of skin saved specifically for batman but it just seems out of character for him to not finish the one on his forehead and just start another one (as far as i know he didn’t kill anyone since asylum until the ak