A player raises to $12 and you say "call" and slide out $12. Everyone else folds, so the pot holds your $12, the raiser's $12 and the $4 in blinds.
You have three nines. The raiser bets $20. You say "raise to 60" before you touch your chips, and the raiser folds.
Your extra $40 comes straight back, because nobody called it. The pot is $68, the house takes $5 in rake and $2 for the jackpot, you tip $1, and $60 comes back to you. You put in $32, so you're up $28.