Shredder Analysis question

I've downloaded Shredder Classic 4, the trial version.  So far, i think its pretty good.  All i want is a program that will analys my games and also be an opponant when i dont have internet coverage.

My question is, when i ask Shredder to suggest a move, it gives me an answer in a split second.  Chessmaster used to ask how long I wanted it to "think" for.  Shredder just punches out an answer.  When Shredder is asked to suggest a move, is it thinking about it at "full strength" or is it only using a processing power equal to the level i am playing against (ie if i set Shredder to play at a 1600 level, it will suggest a move based on a 1600 player)?  I have trouble believing it knows a "best move" straight away.