A complete explanation of Fritz’ “Calculation Feature” can be found at Chessbase.
Part 1, Part 2, Part 3, Part 4
I only discovered this feature the other day while messing around with the program. This feature allows you to take nearly any position and turn it into a kind of problem. After deciding on a position in which to train, you activate the feature.
When you move a piece it's not actually moved on the screen's board. What you do is mentally calculate variations by moving the pieces in your mind's eye just like in a real game. Of course the program doesn't know what you're thinking so you have to "move" the pieces on the board but they don't actually move; they are just recorded in the program's memory.
I tried this out but must be missing something because I took the position from the game below (Fun Blitz Game) after 21… Nc5 and tried calculating some variations.
Although in the initial position White’s supposed to be about 1.5 P’s ahead, I calculated a variation that resulted in equality and received 5 points. So apparently it’s not measuring the worth of the final position, but rather how many errors you made in calculation and/or how serious any gross blunders were. Actually I’m not sure exactly WHAT it’s measuring because next I tried calculating a line where I deliberately made bad moves and finished with an impossible move. It gave me overall score of +1 point…not sure why. I also noticed when I tried making an impossible move it just evaluated up to the point where the impossible move was played.
Unless I totally missed something I don’t see any value in this feature. Looks like a bell (or maybe it's a whistle...who knows?) that could have been left out.