When pickpocketing an NPC and you get caught after the 60+ ish pickpockets at 100% success so then it slowly goes down as you continue unless you click a new NPC it will refresh it..
"The pickpocket target becomes aware of your presence"
So that your chances are less than 100% but there's no way to tell what NPC that message was for if you go afk - get caught - then click the same one?