Well, you'd want the top 176, not 168, but the question still remains.
It gives you more to choose from than just the bottom ten players once you make your way to the end of the draft. If it only listed the top 176, and you drafted based on what you saw at baseballmonster, you'd forget about a lot of players.
Besides, I doubt that through 176 players you'll get exactly 8 of each hitting position and 88 pitchers. I'd be willing to bet the 14th best 1B actually has more value than the 8th best 2B. That's why it'll expand the field.
Your specified league parameters shows 74 players with a positive value, which is close to the midway point of your league's active roster, 88-89. It makes sense, since the top players (Johan, Albert), should have much more positive value than the 176th player should have negative value, since the 8-10 slot at most positions isn't as cut-and-dry as the top at 1B and SP.
All in all, I don't think you need to worry that you're getting inaccurate numbers.