Reverse ascending numbers aggravate the ignorance of the countersign
Reverse ascending numbers - So, thats decending, as in, going down. The Sentry Robot counts sorta like this: 9....8....7...6...5..4..22.214.171.124.
aggravate the ignorance of the - Gets cheezed off (well, if its AI is that advancd) and attacks you because you are ignorant of the password.
countersign - coun*ter*sign, noun - a sign given in reply to another; specifically : a military secret signal that must be given by one wishing to pass a guard. You do the math-err... English.