Winking To Win Book

Before opening my latest book, Winking To Win (Doubles contract credit and money rewards for 31 days), I went and looked at what the mission would currently give, which was 10 credits and 10k cash. So I open the book, go complete the mission, and instead of 20 credits and 20k cash, I got that original 10 credits and 10k cash. Why wasn't it doubled? Bug, or does the book only start working on tonight's newest generated mission? And if that is the case, how would I even know if it doubled? Will it say something to that effect? The only forum thread I could find (https://www.torn.com/forums.php#!p=threads&f=19&t=15984561&b=0&a=0&start=0&to=17300354) mentioned that it doesn't say what the before and after result is.

If you already accepted the mission the book won't double it.

It will affect new missions. Books cannot change what already is.