If my opponent gives up, many times I only get one point instead of two if the player hasn't borne off any pieces. If his pieces on his homeboard I should even get 3 points. But most of the time it's not. But when he plays further till the end of the game and he hasn't borne off any pieces and I win, it's a double game or even a triple one if one of his pieces is still on his homeboard. 
Can anyone explain this to me ?