HOH pot odds

In HOH1, he refers to pot odds as 4 to 1. For example, with K spades and J spades in the hole, and the board showing 2 spades the odds are 4 to 1. I have read others which state this as 1 in 5. As far as I am aware 1 in 5 means you will hit your extra spade card on the turn 1 in 5 times so if you have to call a pot of 500 with 100 then these are exact odds.
However, my understanding of the 4 to 1 against means you wuold call a pot of 400 with 100.
Which is correct?