And Zacchaeus stood and said to the Lord, "Behold, Lord, the half of my goods I give to the poor; and if I have defrauded any one of anything, I restore it fourfold." And Jesus said to him, "Today salvation has come to this house, since he also is a son of Abraham."
The idea behind satisfaction is not that you have to earn forgiveness by doing something to buy it from God. Rather, the idea is that satisfaction – the desire to do something to right a wrong we have done – is the natural outworking (and reward) of penance just as the desire to kiss the beloved is the natural outworking (and reward) of falling in love. A really penitent person does not approach satisfaction as an onerous task, but as something that wild horses couldn't restrain them from doing. Zacchaeus cheated a great many people out of a good deal of money. When he repented of his sin and found forgiveness, he couldn't wait to pay back the people he had cheated. And Jesus did not scold him saying, "My grace is free. You don't have to do that." He rejoiced that Zacchaeus had found salvation and that his salvation had burst out of him in an act of love.