Does the person you attack have to be both unaware and unprepared? Or can they be either unaware and unprepared? I’d personally add an “and” or “or” between them, to clarify which.
Situations I’m thinking of: Someone is aware of your presence but unprepared for you to attack. Or, someone is prepared for you to attack (i.e. on guard), but unaware that you’re lurking right behind them.
EDIT: Also, the 10+ option should be:
10+ = you do it smooth, no one else notices and no traces are left behind
The person you attacked clearly would notice! The word “else” clarifies this, I think. :)