I think the slide should say:

Hey @Ankur_Agarwal1,

I believe there is a small confusion. Let’s define the events. A → Spam Email and B → Email with words “lottery” and “winning”. So, we are trying to find P(A | B), which by Bayes theorem is defined as \frac{P(A ∩ B)}{P(B)}. So, in the denominator we have P(B), which is the probability of email containing words “lottery” and “winning”. Let us know if your issue is resolved.

Cheers,

Elemento