No Limit Theory and Practice (Terms of Expectation)

[MikeyG80]

Just purchased Sklansky and Miller No Limit Theory and Practice and I had a question from page 21 "Thinking in terms of expectation - Playing the nuts on the river"

It gives three examples on the river bet, holding the nuts, of a small bet at $50. A medium sized bet of $150. A large sized bet of $450- All in push. (Take into consideration the example given is from a proposed $5/$10 no limit cash game table where you have $450 left in front of you making this river bet)

It says your expectation for the $50 bet using this formula is $40. $40 = (.80)($50)
expectation for the $150 bet
is $60. $60 = (.40)($150)
expectation for the $450 bet
is $90. $90 = (.20)(450)

What do the amounts of $40, $60 and $90 mean in this example? I'm just a little unclear of these figures and hope i can get a supplement to this example from someone who has this book or knows this example. Is this the amount on average you'll make, in this situation with this much money going into the pot as the bet? It says clearly shown by these amounts, your best move is the all-in push for $450 as it maximizes your expectation.