Theory of Poker Math Question

[Macedon]

To all who have read and digested THEORY OF POKER, I would appreciate some help on some math that was presented on pages 185-186.

In Chapter 19, Sklansky talks about finding the Optimum Bluffing Strategy using Game Theory. Specifically, he states that you should make the odds against you bluffing exactly the same as the pot odds being offered by your bet. That way, your opponent has no idea whether calling or folding is more prudent. The result [from this] is that you produce the optimum strategy against him/her.

Makes sense...right?

But then he introduces the following example:
"Suppose you have a 25% chance of hitting your hand, the pot is $100, and the bet is $100...your opponent is [therefore] getting 2:1 from the pot. Since there is a 25% chance of you making your hand, there should be a 12.5% chance you are bluffing to create the 2-to-1 odds against your bluffing, which is the optimum strategy."

When I do the math, I come up with a different answer. When you add the two percentages together you get 37.5%. That is around 1.7:1 odds, not 2:1. Is Sklansky rounding off?

If you are going by outs, 25% is 3:1, or the equivalent to about 11 outs. 12.5% is 7:1 odds, or a little bit less than 6 outs. Together they add up to 17 outs, or 37%, or 1.7:1. Not 2:1

If you wanted exactly 2:1 odds, shouldn't you add 4 cards (4 outs, or 8.3%) to your 11 out--25% draw, thereby making 2:1 odds (15 outs at 33.3%)?

There is a significant difference between 4 cards and 6 cards, when you are choosing how many cards to bluff on.

Or have I missed something, which I realize is likely?