will casa de apostas

I apologize if this is the wrong spot, I'd appreciate any guidance and where I should post poker theory questions 2️⃣ tied to this book specifically?

I'm looking at the two alpha examples on pages 82 and 83:

Example 1):

9 handed 12.5% ante;Action 2️⃣ folds to hero in the SB with 72o and an overly tight player in BB. What's the alpha if we 2️⃣ raise 2.5bb from the SB?

They proceed to show alpha as 2/(2+2.625)=0.43.