odds calculated with 47 vs 45 unseen cards?

[CanadaLowball]

whats the deal with that? in Sklansky's Hold'em Poker, he mentions something about "no-limit insurance", but he does not explain exactly what that means...

for example, in the case of flush draws, the way i was taught was if i had a flush draw on the flop, i've got 9 outs to hit it, so my % to win with a flush is 1 - (38/47)(37/46) = ~35%

why would i calculate it as 1 - (36/45)(35/44)? which is the way Phil Gordon also used to make his table at the back of his Little Green Book..

there's something i'm not exactly understanding and its bugging the hell out of me

[RevAgain]

Only thing that springs to mind is it's assumed your opponent has none of the flush suit. If it's part of an example hand this would make sense.

[LouisCyphre]

Insurance means that if two players are all-in the player who is in front makes a side-bet that he will lose the hand.
That way he will show a profit no matter what happens.
Considering this calculating the odds with only 45 unknown cards makes sense because your opponent will have revealed his hole cards. A common scenario is a set vs. a flush draw.