How do the numbers on hacking progress work?

[contingencyplan]

So in my current game, I have a +110.88 hacking progress (HaP), but it is
currently listing my Expected Hacking Response Level as "337 (Very High)".
What is the algorithm for determining hacking response? I thought (but could
be wrong) that the only time that the response really escalates is when the
HaP goes negative. So with 100 points left, why is the AI response "Very
High"?

[PokerChen]

The response is currently based on (AIP - HaP), as far as I recall.  0 HaP remains the breakpoint where it begins to increase exponentially.