Confusion about this example

From the book Theory of Poker Applied to No-Limit, chapter on Pot Odds page 43

”When you have a moderate stack (or your opponent does) and you think your chances are somewhat below 50% to win, at best, you might contemplate moving all-in on his bet. But before doing this, you must calculate the real odds you’re getting.
For example, if your opponent bets $100 into a $200 pot and your stack is $250, your move-in means that the odds you’re really getting are not 3-to-1 but rather $450-to-$250, or 1.8-to-1. If you think you’ll win one out of three, that extra money in your stack probably turns a call into a fold. That’s because you’re usually going to have to put your last $150 into the pot at the last moment anyway. (Note: We’re assuming your opponent won’t fold when he’s raised $150.)
• On the other hand, if the one-out-of-three chance mentioned above was a drawing hand that would rarely lose if it hits, the situation reverses. A raise would be wrong unless you somehow thought it might get him to fold. But you can call and bet the rest only if you hit. Now your odds are actually almost $450-to-$100, or 4.5-to-1. So, a one-third chance would be more than enough.
• Your pot odds are not as good as you think they are when there is a decent likelihood of a raise behind you.”

Is this correct? I am confused. I can’t understand the example.