This particular game has four regions that tie into a middle region through one cell. The difference between the horizontal and vertical members of each of the four outside regions produces the cells that are highlighted. Two of the regions have a vertical sum that is larger and the other two regions have a horizontal sum that is larger, depending on which kind of member (horizontal/vertical) joins the middle region.
The top left region has horizontal members of 10, 14, 24, 22, 10 and 7 which add up to 87.
The vertical members are 12, 15, 30, 8, 11 and 12 which add up to 88.
88 - 87 = 1