Sklansky and bluffing odds

Hi, everyone, I am fairly new to poker and have begun reading Sklansky's theory of poker. I was wondering if anyone can translate this paragraph for me:

"When using game theory to decide whether to call a possible bluff--assuming your hand can beat only a bluff and assuming your judgement doesn't give you a hint--you must determine the odds your opponent is getting on a bluff. Make the ratio of the calls to your folds the same as those odds. If your opponent is getting 4 to 1 odds on a bluff, you must call randomly four out of five times to make that bluffing unprofitable."

All I need to know is what it means to "get 4 to 1 odds on a bluff" Does that mean 4 times it isn't a bluff and one time it is, or vice versa? Or does it mean neither of those two things. Much help appreciated.

Denouement

I think he mentions this elsewhere in the text. Basically it means that if the pot is $80 and the opponent bluffs, betting $20, he's getting 4-1 on his bluff. It means that if he wins 2 of those pots he's showing a significant ($80) profit.