Starting ability score adjustments are listed in two ways. First, they show the actual adjustment as compared with the base "human" starting ability scores. Then, in parentheses, the ESA, or Effective Stat Adjustment, is listed, showing the actual changes the skin makes on top of whatever ability score modifiers the standard race already comes with. For instance, the half giant race, as compared to a human (which starts with no ability score adjustments) starts out with a +5 Strength, +4 Constitution, -6 Intelligence, -6 Charisma. However, the standard race used to create a half giant is the half orc, not a human. Half orcs, as compared with humans, start off with a +2 Strength, -2 Intelligence, and -2 Charisma. So, the ESA listed in the Half giant description states that the in-game template (skin) actually applies a +3 Strength, +4 Constitution, -4 Intelligence, and -4 Charisma. Add the ESA to the starting adjustments of the half orc and it's obvious that together they match the starting ability score adjustments for a half giant.