An integer is a whole number that can be positive, negative, or zero. For example ...-3,-2,-1,0,1,2,3....
Here, positive value indicates gain or above something where as negative value indicates loss or below something.
If the change in the value of his favorite card is $-7, that simply indicates that he is having a loss of $-7 that can be understand as the value of his this years card must be smaller than the last year card.
